Pastry cream or crème patissière is a staple in pastry kitchens and originated in France. This versatile cream is used to fill cream puffs, éclairs, Napoléons, tarts, and other pastries. It is spread in between cake layers, such as Boston Cream Pie, and using as a base for endless recipes. It is called the "Mother of all creams!"  

Pastry Cream a rich, thick stirred custard, cooked on the stove, made from a mixture of milk or cream, eggs, sugar, flour (roux) and/or cornstarch. 

Pastry Cream is versatile and can be easily flavored with vanilla beans, liqueurs, coffee and fruit purees are some complementary flavorings are often added. Heavy whipping cream can be folded in to the Pastry Cream once its cooled for a richer and fluffier cream. You can easily make chocolate pastry cream by adding a couple of ounces of bittersweet or semi-sweet dark chocolate to the base recipe along with the vanilla. Another flavoring option is to add a tablespoon or so of a flavored liqueuer such as Frangelico, Chambord, Kahlua or crème de cacao or others. Gourmet shops will also have flavored nut pastes such as hazelnut or almond which can be used to flavor the pastry cream.

The main thickener for Pastry Cream is eggs, but it gets some help from cornstarch or roux (typically a mixture of fat and flour heated and used as a basis for sauces, but in this case, just flour). Eggs make it smooth and rich, but can also curdle if heated too much. Gentle heating is the way to go. Here’s what’s going on: When eggs are heated, their proteins unwind, then join with other unwound proteins. This causes the proteins to get thicker — the longer they’re heated, the more tightly they join and the thicker they get. Gentle cooking (like poaching) keeps the egg proteins loose. If the heat’s turned up, the proteins will seize up and you’ll have scrambled eggs.

PASTRY CREAM TIPS:

Do not make Pastry Cream in an aluminum pot because it gives a grayish coloration to it.

If the heat is too high or you are stirring too slow at the point when the pastry cream reaches a boil, it will lump. If this happens, pass it through a strainer immediately, before it cools.

When removing the cooked Pastry Cream from the pot to another container, do not scrape the bottom of the pan. You often see a layer of the cooked or burned mixture on the bottom of the pan and you don't want to mix it in with the good stuff.

Always strain your Pastry Cream while still warm through a fine mesh strainer before chilling. You want to make sure you strain out the small lumps which are really the chalazae parts of the egg.

Once made and while still warm, press plastic wrap directly on the surface of the Pastry Cream, and refrigerate until cold and set, at least 3 hours or up to 2 days. Chilling thickens the filling, so make it first, then make the rest of the recipe. But don’t whisk the cold Pastry Cream — it breaks down the starch, thinning it.

Never leave a recipe that includes Pastry Cream out on a hot day; it is an ideal mixture for bacteria! Refrigerate cakes or any recipe made with pastry cream fillings or whipped cream frostings immediately. You can freeze cakes with filled with pastry cream, but it won't be quite the same nice texture as before and may make the cake soggy. Remember to thaw and then store the cake in the refrigerator.

Technical Stages of Making Cornstarch-Thickened Pastry Cream: Combine cornstarch with some sugar and milk, add egg yolks, incorporate this mixture into a separate pot of hot milk and sugar, cook slowly until thickened. Finish with vanilla extract and butter. The result is a velvety smooth custard that spreads without being runny.

Technical Stages of Making Roux-Thickened Pastry Cream: This type of pastry cream is made by thickening sweet milk with a white roux and tempering in the yolks. If vanilla extract were to be used, it would be added at the end. The mixture starts out as stiff, but obtains a sauce-like consistency when the added sugar melts and becomes fluid. The egg yolks add fat and lecithin or silkiness and color and flavor.

1. Bring the milk to a boiling point. If vanilla beans are used to flavor the milk, add here spliced lengthwise.
2. Mix the yolks and sugar and whisk until pale and light.
3. Add the flour.
4. As soon as the milk starts to boil pour at once the milk on the egg yolks, whisking.
5. Transfer back into the milk pot and cook for 4 to 5 minutes, constantly stirring and making sure the cream doesn't stick to the bottom.
6. Empty the cream in a bowl. Take a piece of plastic wrap plastic film pushed on the surface of the cream to avoid the formation of a crust on the surface. It is also possible to brush the surface of the cream with some butter and then cover.