Return it to the pan and cook until it’s a thick pudding consistency. Remove from the heat, and whisk in the butter and vanilla extract. Transfer to a bowl, plastic wrap, and refrigerate until set (2 hours minimum)
Make the Cupcakes:
Mix flour, sugar, baking powder & Salt. Add butter; and mix, then eggs. Add milk and vanilla; mix until smooth. Fill muffin cups. Bake about 19-20 minutes at 350 degrees F then let cool for 5 minutes.