Custard's Last Stand
You're making pastry cream for a banana cream pie for dessert tomorrow. Chilling it overnight should render it appetizingly
You're making pastry cream for a banana cream pie for dessert tomorrow. Chilling it overnight should render it appetizingly cold by tomorrow. Dinner concludes and it's time for the piece de résistance.
To a herald of "oohs" and "as" you present your luscious banana cream pie. But when you cut into it, you discover a runny mess. Beneath the decadently deceptive whipped cream topping is a puddle of ooze. What went wrong?
Most likely you never brought your pastry cream to a full boil. Pastry cream is a custard, (an egg and milk mixture), thickened with flour or cornstarch.
The starch, which imparts the cream with structure, contains a carbohydrate compound called amylose. Raw eggs contain an enzyme called alpha amylase that devours amylose. Boiling destroys the enzyme.
Much like the famed Calvary general, your troops, (the amylose), were overrun by the Indians, (the alpha amylase), because you didn't wait for reinforcements, (extra heat). With the amylose defeated, nothing was left standing.
A custard is a mixture of eggs and milk and/or cream that can be hot or cold, sweet or savory. Most custards are desserts such as creme brulee, flan, and cheesecake. Quiche however, is a savory custard.
Custards can be stirred on the stovetop or baked in the oven. Classic stirred custards include creme anglaise and pastry cream, a.k.a. crime petissiere. Creme anglaise does not contain starch and thus is more fluid.
It is used as a sauce over cakes or fruit. Pastry cream, as stated, contains starch and therefore more body. It is used to fill tarts, Napoleons, cream puffs, éclairs and cream pies.
Despite my introductory example of a failed pastry cream, crime anglaise is actually the trickier of the two. The starch in pastry cream not only thickens it, it prevents curdling by interfering with the coagulation of the proteins.
Creme anglaise, devoid of such protection can curdle very easily. Thus, while pastry cream must be brought to a full boil, crime anglaise must be gently cooked until it reaches a temperature of 170-175 degrees.
It curdles at 180 so the window of success is quite narrow. Some chefs employ a double boiler, (a metal bowl resting on top of a saucepan of simmering water), which produces a more gentle heat than direct cooking in a saucepan.
Baked custards include crime brulee, flan, cheesecake, and quiche. With the exception of quiche, baked custards are usually cooked in a water bath.
Once again, gentle heating is required to prevent curdling. The water bath insulates the custard from excessive heat. Baked custards are usually poured into ramekins resting inside a roasting pan filled with enough water to come halfway up the sides of the ramekins.
They are done when they evince no more than a slight wiggle when the pan is shaken. It is better to slightly undercooked them since carry over cooking will take place. If overdone they crack or curdle.