Crème Anglais

from Joy of Cooking

Whisk together in a medium bowl until slightly thickened:
6 large egg yolks
1/3 to 1/2 cup sugar
Pour into a medium, heavy saucepan:
2 cups whole milk, 1 cup whole milk and 1 cup light or heavy cream or 2 cups half & half
(Really, even low-fat milk works here)
Cook, stirring, over medium heat until bubbles form around the edges. Slowly whisk the hot milk into the egg yolks and sugar. Return this mixture to the saucepan. Rinse out and dry the mixing bowl, then set a fine-mesh sieve over the top. Place the saucepan over low heat. Using a heatproof spatula or a wooden spoon, stir the sauce gently but constantly, sweeping the entire pan bottom and reaching into the corners. As soon as the sauce is slightly thickened, remove the pan from the heat and stir for 2 minutes to complete the cooking. The sauce should be the consistency of heavy cream and register around 170ºF on an instant-read thermometer. Pour the sauce through the sieve and let cook for 10 minutes, stirring periodically to prevent a skin from forming. Stir in:
2 teaspoons vanilla
Serve warm or cold. If chilling, let the sauce become completely cold before covering, as condensation will cause it to thin. The sauce can be covered and refrigerated for up to 3 days. To reheat, set the container of sauce in water heated to 165ºF and stir until warmed through.