From America's Test Kitchen
This simple, classic French dessert is essentially a baked custard, but what makes it really stand out is the caramel sauce. We found that making the caramel is relatively simple; what we needed to address was the custard, which should be silky smooth, modestly sweet, and firm but not rubbery.
We discovered that the proportion of egg whites to yolks in the custard was critical for the texture. Too many whites caused the custard to solidify too much, and too few left it almost runny. We settled on a formula of three whole eggs and two yolks. Light cream and milk for the dairy component provided the proper amount of richness. For contrast with the sweet caramel, we kept the amount of sugar in the custard to a minimum. The caramel comes together quickly; sugar is dissolved in water and cooked until caramel-colored. Baking the ramekins in a water bath was essential for even cooking and ensured a delicate custard; a dish towel on the bottom of the pan stabilized the ramekins and prevented the bottoms of the custards from overcooking. When we unmolded our crème caramel on serving plates, the sweet caramel sauce bathed the rounds of perfectly cooked custard.
Though you can make one large creme caramel, we find that custards baked in individual ramekins cook faster, are more evenly textured, and unmold more easily. You can vary the amount of sugar in the custard to suit your taste. Most tasters preferred the full two-thirds cup, but you can reduce that amount to as little as one-half cup to create a greater contrast between the custard and the sweetness of the caramel. Cook the caramel in a pan with a light-colored interior, since a dark surface makes it difficult to judge the color of the syrup. Caramel can leave a real mess in a pan, but it is easy to clean. Simply boil lots of water in the pan for 5 to 10 minutes to loosen the hardened caramel. Espresso beans ground in a coffee grinder will be too fine and impart too strong a coffee flavor to the custard. Instead, crush the beans lightly with the bottom of a heavy saucepan.