Sunday, March 6, 2011

P Is For Pastry Cream and Pate Choux

For about 18 hours in 1980 I considered going to medical school.  I decided against it based on two facts:  I had already recieved a B in a class and figured that would prevent me from becoming a doctor, and (more importantly) I read in the curriculum that I would have to take Chemistry.  Deal breaker.  Here's the thing with Chemistry...ask anyone who has taken a chemistry class about it and all they say is "math, lots of math"  To this day (because I still have not ever taken a chemistry class) when I ask people about chemistry, that is their response..."math, lots of math."  (Sometimes I will ask students what they think about their chemistry class just to see if they give me the same answer...and they almost always do.)

Math?  Really?  That answer has always frustrated me.  Firstly, because math has been a lifelong nemesis.  Numbers, no matter if they are in dollar form, ratios, percentages, sale prices, or weights and measures, apparently are processed in a part of my brain that is lacking in dendritic density.  No matter how simple the calculation, I have to write it down, study it, do it wrong a few times, get frustrated, do it again, and then it all makes sense...maybe.  (F'rinstance, yesterday Nik was explaining the cell phone plan options that he was considering...a $129 cancellation fee with a 10% monthly discount versus the new plan which was cheaper monthly but required an activiation fee of blah blah blah.  It was like he was speaking some illogical foreign tongue.  I felt like my brain actually turned off after about 30 seconds of listening to him.)

But the math conundrum is not the most irritating part of the chemistry=math answer.  Maybe I am naive, but I thought that chemistry was learning about the elemental components of everything.  For a fact freak like me, what could be more interesting than that?  To learn how a relative handful of stuff can be combined to create everything in the world...well that pretty much sounds like the key to all knowledge, doesn't it?  I admit that the numbers and letters on the Periodic Table of Elements are quite meaningless to me...but I do understand the basic concept behind it and that excites me.  It's a Table of What Could Be.  (So you can see my disappointment when someone throws cold H2O on this excitement by reducing it all to dreaded Math.)  I keep threatening to take a Chemistry 101 class at the local community college...just to prove to these Math Terrorists, and myself, that there is more to Creation than math, hopefully.

But hold on just a moment...a recipe is essentially a Table of Elements, a Culinary Table of Elements.  Replace articulatory mouthfuls such as Darmstadtium, Ununpentium, Seaborgium, and Xenon for bowls of more flavorful items such as Flour, Butter, Eggs, Chocolate, Yeast, and Salt and what do you have?  You have a very approachable and delicious Table of Potential.  Wandering the stalls at a farmer's market, or flipping through the pages of a cookbook or food magazine, I don't find myself drooling and thinking "I want to eat that."  I am saying to myself..."I want to make that."  And with  a pantry full of basic elemental ingredients - I can do that.

But the potential goes beyond even that, beyond individual ingredients...because if you make a batch of this and you make pan of that, you can put them together to make an entirely different and tasty this-and-that.  (Nik's pet peeve with the old Joy Of Cooking was it's tendency to list page numbers for other recipes in it's list of ingredients for a dish.  Different strokes.  I see a complex list of ingredients and preparations and I put a star next to that recipe as a Must Do.)  So while flour and eggs and butter are essential ingredients for thousands of baked goods, every baker also knows that equally important are fundamental preparations such as custards, and laminated doughs, and meringues, and shortdoughs.  And here's the irony to this tale...every baker needs to know a little bit of practical chemistry as well to make it all work. 

Take pastry cream, for's all about chemistry.  Pastry cream is 1) a stirred custard and 2) one of a baker's multi-use items.  Peek down to the recipe below, step #5, and you will see that it instructs you to let this mixture of eggs and milk bubble and cook for a minute.  WHAT?  Anyone who has ever made breakfast knows that cooking eggs till they bubble will create scrambled eggs and not a luscious creamy custard.  Enter Chemistry. 

Pastry cream contains eggs, sugar, milk, and cornstarch.  While the temperature in the saucepan is rising, the egg proteins are unravelling from compact little pearls of albumin into long graceful strands that sweep and swirl around in the liquid surrounding them.  In a concentrated mixture, just a bowl of eggs say, these unravelled proteins would bond (a chemistry term) with each other quickly, firmy, and efficiently (think scrambled eggs).  But the milk in the pastry cream formula dilutes the mixture, putting more space and stuff between the egg-protein molecules (Molecules? Chemistry again).  Think of it like this...10 kids playing Marco Polo in a kiddie pool are bound to find each other quickly...Game Over.  Put those same 10 kids in an Olympic sized swmming pool and that game could go on all day (ugh).  But there's more chemistry here...the sugar in the mixture coats the proteins (there are several thousand sugar molecules for each lonely protein molecule) making bonding less likely when the proteins do get close to each other. 

Of course, ultimately the proteins will bond (because that's the whole point in cooking them) BUT, just like those kids in the pool, there is alot of liquid slopping around in the spaces between the proteins.  And that's why we add cornstarch to pastry cream.  As the mixture is heating and the proteins are unravelling and shouting out "Marco" and "Polo" to each other, the cornstarch is likewise getting hot and it starts to sweat its guts out.  Cornstarch sweats a thickening agent that floats through the pastry cream mixture and via "hydrogen bonding" (Chemisty!) it captures water molecules.  And the hotter it gets (until around 200 degrees) the more it sweats and the more water it traps.  The mixture thickens as the water is trapped and the proteins bond, and that's when you turn the heat off and chill those hard working, exhausted molecules.  Ahh yes, just as I thought...Chemistry is possible without Math, but Cooking is all about Chemistry.

So we start with eggs and butter and dairy and a starch, and we make a basic custard and a simple pastry dough, and to them we can add whipped cream or more butter or  chocolate or praline paste or cheese or any number of other ingredients or preparations and instead of a plate of eclairs, you can have cream puffs, or beignets, or gougere, buttercream, or crab puffs, or Paris Brest.  The possibilities are truly endless.

Pastry Cream
Whole Milk                  2 cups
Granulated Sugar          4 oz (or about 1/2 cup), divided
Cornstarch                  50 grams (or about 3 1/2 Tbsp)
Salt                            1/4 tsp
Eggs                           2
Vanilla                        1 1/2 tsp
Butter                        2 oz

1.  Combine the milk and approx 1/2 the sugar in a saucepan, and bring to a simmer.
2.  While the milk is warming, combine the remaining sugar, the cornstarch and the salt in a mixing bowl.  Set it on a damp towel or rubberized something - so it won't scoot across the counter when both your hands are busy and you can't steady the bowl.
3.  When the milk is almost hot enough, whisk the eggs into the sugar-cornstarch mixture until smooth.
4.  Immediately add a little of the hot milk mixture to the egg mixture, whisking constantly.  Keep adding and whisking until more than half the milk has been added, then return the saucepan to the heat, and whisk the warmed egg-milk mixture back into the saucepan.  Turn burner to medium-low. 
5.  Whisk or stir slowly until the mixture thickens (about 4-5 minutes).  Turn the heat down a bit if it is cooking too quickly on the bottom. (Nobody likes scorched pastry cream.)  Let it bubble for about a minute, stirring or whisking steadily. 
6.  Remove from the heat, stir in the vanilla and the butter.
7.  Put the pastry cream into a bowl, and put that bowl in a larger bowl of ice water.  Lay a piece of plastic wrap directly on the top of the pastry cream, to prevent a skin from forming.  Keep chilled in the refrigerator until ready to use. 

Pastry Cream - Chocolate Variation
Melt 7 ounces of buttersweet chocolate.
At Step 7 of the recipe above, reduce the amount of butter to 1 ounce and stir in the melted chocolate with the vanilla and butter.

Pate Choux
Cake Flour             4 oz
Bread Flour            5 1/2 oz
Water                   2 cups
Unsalted Butter      6 oz
Salt                       1/2 tsp
Eggs                      8

1.  In a saucepan, bring the water, salt and butter to a full boil.
2.  While the water is heating, combine the flours and set aside.
3.  When the water is at a boil, remove from the heat and add the flour, stirring thoroughly until all the flour is moistened.
4.  Return the pan to the medium heat and cook, stirring constantly, until the mixture forms a mass, and the flour forms a light skin on the bottom of the pan.  Remove from the heat. 
5.  Let the dough cool briefly until it is very-warm to the touch.  (You can add the eggs by hand or put the dough in the stand mixer and let it do the work.)  Either way, add the eggs one at a time, mixing thoroughly after each addition, until the dough is soft but still holds its shape.  (Egg Test:  Take a blob of dough on your spatula and turn it upside down -- if it elongates and forms a "V" shape, you have added enough eggs.  It if is too stiff to elongate, you need to add another egg.)
6.  For mini-eclairs, use a 3/4-inch piping tip and pipe the dough into approx. 4 inch lengths on a Silpat.  If they have a little flip at the end (like the ones in the picture), wet your fingertip slightly and flatten the flip before baking.
7.  Bake at 425 degrees for 10 minutes, then reduce the heat to 375 degree and bake until they are lightly browned and have a slightly crisp exterior (about 20 minutes). 



Jackie said...

Why so hard on math?! It sounds to me like you've just been doing applied math - I think that must be your problem. If you ever take that chemistry class, I'll help you balance your equations:)

The A Team said...

Yummy! Thanks for the explanation! See- if Chem teachers could lecture like that, everyone would understand it! Bravo!

The A Team said...

Yummy! Thanks for the explanation! See- if Chem teachers could lecture like that, everyone would understand it! Bravo!