When we lived in England, my husband loved some little custard tarts that we would buy from a Portuguese bakery in the town in which we lived. Since then, I have been attempting to re-create them to his satisfaction. Recently, I was testing a recipe from Emeril Lagasse and it turned out to be a winner. Hurray! This testing caused me to think about custard and what a wonderful creation it is. It is something all cooks should know how to do and this is why I am writing 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 for these little Portuguese tartlets but a custard is also the basis of crème brûlée, 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.
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, my tartlet recipe had me infuse vanilla seeds and orange zest into the milk. This was achieved by bringing the cream to a boil, adding those two ingredients, covering it, taking it off the heat and allowing to steep for 30 minutes. I then whisked that steeped dairy into my 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 recipe will instruct you to heat it so as to cook the eggs and thicken the mixture. This heating should be done very gently. 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.
Some custards are meant to be very soft and creamy while others (such as those that need to be turned out of the container before serving) are firmer. This 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 even yolks alone) produces a softer, creamier custard.
Some recipes will have you add a starch such as flour or cornstarch. These ingredients help with thickening while also protecting 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. 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. On the other hand, if you do add a starch to the mixture, the custard can be cooked over direct heat on the stovetop or without a water bath in the oven.
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.
All this talk of custards has me salivating over those little Portuguese custard tartlets that I made. I have a few left and those will definitely be dessert tonight! How about you? Is a custard in your near future? Let me know!