In the microwave, heat the milk and cream for 2 minutes to warm up.
In a saucepan, whisk together the egg yolks, cornstarch, and sugar until thick and pale yellow, about 2 minutes.
Slowly whisk in the warm milk and cream and place saucepan over medium-low heat. Bring to a simmer while slowly stirring sauce with a large spoon. Cook, while stirring, for about 4 minutes or until the sauce is thick enough to coat the back of the spoon. Stir in the vanilla paste.
Pour sauce into bowl and cover with plastic wrap, pressing it directly onto the surface to prevent a skin from forming on the sauce, and refrigerate.
Sauce can be made up to 2 days in advance.
Makes 2 cups.