Place the milk in a heavy nonreactive medium saucepan, scrape the half vanilla bean seeds in, and bring to a boil over medium-high heat. Let the mixture rise up the side of the pan, then immediately remove from the heat.

Meanwhile, in the bowl of an electric mixer fitted with the whisk attachment, beat the egg yolks with the sugar on high speed until very thick and pale, about 3 to 4 minutes. The mixture will triple in volume and form a ribbon when dropped from the whisk.

Bring the bowl over to the saucepan. Whisk about 1 cup of the hot milk into the yolk mixture to temper it, then pour the mixture back into the saucepan. Off heat, stir until the custard is thick enough to coat a wooden spoon. (Run your finger through the custard on the back of the spoon. The custard is thick enough when the line remains.) Immediately pour the crème anglaise through a China cap or fine-mesh strainer into a bowl and whisk until cool. Refrigerate for up to 3 days. Cover after completely cool.