In a saucepan, heat the milk, sugar, and vanilla until small bubbles form around the edge. In a separate bowl, whisk the egg yolks and cornstarch until smooth. Gradually whisk the hot milk mixture into the egg yolk mixture, then pour the whole mixture back into the saucepan.
2 cups Milk, ½ cup Sugar, 2 tsp. Vanilla Extract, 4 Egg Yolks, 3 tbsp. Cornstarch