Heat milk in medium saucepan over medium heat just to boiling.
Whisk egg yolks and sugar together in medium bowl. Gradually whisk in hot milk. Return mixture to sauce pan and cook, stirring constantly over medium/low heat, until it thickens and coats the back of a spoon about 6 minutes.
DO NOT BOIL! Strain through a sieve into a mixer bowl. Stir in coffee powder and vanilla and let set to room temperature. Beat in 2 cups butter, 1 Tbsp at a time, beating well after each addiction.
Servings: Servings: