Mocha filling

This is mocha filling for cake. Another version. I haven't actually tasted cake filled with it yet, but I need to write it down before I forget. Initially based on http://www.wilton.com/recipe/Chocolate-Filling-1

3 tablespoons all-purpose flour
1/2 teaspoon salt
3/4 cup granulated sugar
4 tsp instant coffee powder
1 cup half & half
5 egg yolks
1/2 teaspoons pure vanilla extract
1/2 cup chocolate chips
Makes: About 1 1/2 cups of filling.


instructions
Mix the flour, salt, instant coffee and sugar in a saucepan and blend in a little of the cream. Place on medium heat and stir constantly. Add the rest of the cream and and continue stirring until the mixture reaches the consistency of medium cream sauce. Stir a little of the sauce into the egg yolks, then pour egg yolks into the sauce in pan. Cook for a few minutes on low heat until thickened. Remove from heat, add unsweetened chocolate to the mixture along with the vanilla and cool quickly. To prevent a skin from forming, brush with melted butter. Stir a little before using