1. Heat the milk and vanilla bean, if using, in a medium saucepan until it bubbles form around the edges. Remove from the heat and let stand for 10 minutes. Using the tip of a knife, scrape half of the seeds from the bean into the milk. Rinse the vanilla bean and save for another use.

2. Beat the yolks and sugar in a heatproof bowl. Gradually whisk in the hot milk. Rinse and dry the saucepan, and return the milk mixture to the pan.

3. Cook over medium-low heat, stirring constantly with a wooden spoon, until the custard is thick enough to coat the spoon (an instant-read thermometer will read 185°F (85°C)). Do not boil.

4. Strain through a sieve into a bowl. If not using the vanilla bean, stir in the vanilla extract. To serve warm, use immediately. Or place plastic wrap directly on the surface, pierce a few holes in the wrap, and let cool.

Variation: Citrus Crème Anglaise

Add the grated zest of 1 lemon or orange to the strained custard.