I have been working on a class I will be teaching on Crêpes. In the class, I will be teaching how to make different varieties of crêpes as well as numerous fillings, both savory and sweet. One of the sweet ones is an Orange Custard filling. Custards are delicious and wonderful creations and it is a technique that all cooks should know. That is the subject of this Cooking Tip.
A custard is nothing more than a mixture of milk, eggs and often sugar that is cooked into a thickened product. It forms the filling not only for crêpes but also is the basis of crème brulee, flan, ice cream, quiche and more. It is not difficult to make a custard but there are some hints that I hope you find helpful. I also recommend that you invest in a good instant read thermometer as it will help you make a delicious custard that is safe to eat but not overcooked.
Custards can be categorized in a couple different ways. The first is by the cooking technique.
- Baked custards are typically started on the stovetop but baked in the oven. Examples are crème brûlée, flan and cheesecake.
- Stovetop (stirred) custards are, as the name implies, cooked totally on the cooktop. These custards are smooth, creamy and thickened but do not gel as with a baked custard. Examples are crème anglaise, pastry cream and zabaglione.
The other way to categorize custards is by how they are thickened.
- Basic custards – thickened by eggs alone. They are delicate and care must be taken to not overcook them. They thicken between 160° and 180°F. Cooking it beyond 185°F may cause it to curdle and lose its shape as the egg proteins break down. You also run the risk of creating scrambled eggs. To prevent this, these custards are usually cooked by using a double boiler. They should never be boiled.
These custards are meant to be very soft and creamy although the thickness can be adjusted by changing the proportion of the egg content. If you use more whole eggs or egg whites, the custard will turn out firmer and glossier. More egg yolks (or yolks alone) produce a softer, creamier custard.
Examples – crème anglaise (which can be frozen into ice cream), flan, pot de crème, crème caramel.
- Starch-thickened – this type of custard is thickened with the aid of a starch such as flour or cornstarch. They have more body and are not quite as delicate as the starch helps to protect against curdling. The recommended amount is one tablespoon of flour or two teaspoons cornstarch (or arrowroot) for every cup of liquid. Whereas this does help guard against curdling, it can also turn a smooth, creamy dish into a thicker and coarser one. This type of custard needs to be brought to a simmer to ensure it is cooked properly. A guideline is to cook it for 1-2 minutes after bubbles appear. For more information types of thickeners, see the Tip.
Examples – puddings, pastry cream, cheesecake.
- Gelatin-set – gelatin is used to produce a set-up custard that can stand on its own after it has been chilled properly. I love using leaf gelatin rather than powdered for the silkiest texture. See this Tip for more info on gelatin types.
Examples – a classic example is a Bavarian, which is usually set in a decorative mold. A basic custard may also have gelatin added to it, often along with a fruit puree or chocolate. It then can be made into an icebox pie.
Now for some technique advice. Many custards start by having you beat/whisk the eggs (whole or just yolks) together with the sugar until it has thickened and turned light yellow. Some will recommend you continue to the “ribbon” stage, which means the mixture will form a ribbon as you lift up your spoon and allow the mixture to fall back into the bowl. These instructions are meant to help you ensure that the sugar has mostly dissolved. You do not necessarily need to go all the way to ribbon stage but a good mixing until the color and consistency changes is a good idea.
Some recipes will have you heat the dairy (milk, cream) before adding it to the egg/sugar mixture. This is not necessary unless you want to infuse flavor into the dairy. For example, I have a custard tart recipe in which I infuse vanilla seeds and orange zest into milk. This is achieved by bringing the dairy to a boil, adding those two ingredients, covering it, taking it off the heat and allowing to steep for 30 minutes. That steeped dairy is then whisked into the egg mixture. If I did not want to infuse any flavors, I could have added everything together and then heated it on the stovetop.
If you are told to add hot milk/cream to the egg mixture, the danger is that the eggs will start to cook and you will end up with a scrambled egg mixture. To avoid this, you should “temper” the hot liquid into the eggs. This simply means adding some of the hot liquid very slowly into the eggs while whisking. Once the eggs have been diluted with the dairy, you can put it all back into the pot and continue with the recipe.
If your egg/dairy mixture is started cold, the heating should be done very gently so as not cook the eggs but still thicken the mixture. Resist the temptation to turn up the heat to speed the process. I love how Harold McGee puts it in his book, On Food and Cooking.
“Turning up the heat is like accelerating on a wet road while you’re looking for an unfamiliar driveway. You get to your destination faster, but you may not be able to brake in time to avoid skidding past it.”
As he goes on to explain, the chemical reactions that cause the thickening of the custard don’t stop just because you take it off the heat. So, if you try to hurry this step, you may easily get to the point of curdling or overcooking.
Whether your custard is made totally on the stovetop or ends up in the oven, if there is no starch in it, it requires gentle heating. On a stovetop, this generally means using the double boiler method with constant stirring. If in the oven, a water bath should be used. A water bath just means putting the custard dishes in a larger pan (such as a roasting pan) that has enough hot water in it to go up about half-way the height of the custard dishes. Even though your oven temperature may be set at 350°F, the water in the pan won’t exceed 212°F (or even less if you live at altitude). This means the custards are exposed to a gentler & more even heat. Some recommend putting a rack in the bottom upon which you place the custard dishes so that they are not directly exposed to the hot bottom of the pan. Without a water bath, the outside of your custard could overcook before the center is done. With a water bath, you are more likely to catch them at the perfect degree of doneness.
If you are concerned about egg safety, you may be wondering if the eggs in a stovetop custard are cooked enough to sterilize them. As long as the mixture is cooked to at least 160°F, you will be fine. As mentioned above, you do not want the mixture to go above 185° or it might curdle. A basic crème anglaise should be ready between 175°-180°F but some recommend taking it to 180-185°F if using it to make ice cream as it will be a bit thicker.
Baked custards should come out of the oven when they are still jiggling when gently shaken, which will be around 170°-175°F.
Who doesn’t love a custardy dish? Whether you want to make a savory quiche, a chocolate pudding or an elegant crème brûlée, I trust this Tip will help you impress your friends/family.