Homemade custard is a great addition to so many desserts — like our Open-Faced Apple Pie — and this version is redolent of exotic vanilla. Custard can be tricky to make because if the eggs get too hot, they’ll scramble; here the addition of cornstarch makes the custard thick and virtually fool-proof. If you prefer a looser, more traditional custard, eliminate the cornstarch and use a double boiler to cook the base.
Combine the milk, cream, and vanilla bean (or vanilla paste) in a heavy-bottom sauce pan and bring to the start of a simmer over low heat. Turn off the heat and let the mixture sit for 10 minutes to infuse it with vanilla flavor.
In a large bowl, whisk together the egg yolks and sugar. In a small bowl, mix the cornstarch with 2 teaspoons of water to create a smooth slurry. Add the slurry to the egg-sugar mixture. Pour the hot milk (with the vanilla bean, if using) into the bowl and whisk to combine. Transfer the custard base back to the saucepan and cook over low heat, stirring constantly, until the custard thickens, about 10 minutes.
Remove the vanilla bean from the custard and scrape out the seeds with a small knife. Add the seeds to the custard, then rinse the vanilla pod and reserve it for another use. If the custard is at all lumpy, pass it through a fine mesh sieve. Serve hot.