-
Preheat oven to 400F.
-
Place semi-sweet chocolate chips and butter in a microwave safe bowl.
-
Microwave on medium (50% power) for 1 minute, and stir; microwave at additional 30 second intervals, stirring each time, until chocolate is melted, but do not scorch (cooking time may vary with different ovens, but about 3 minutes total).
-
Allow chocolate to cool about 10 minutes.
-
Stir chocolate together with buttermilk, sugar, egg, and vanilla.
-
Separately, sift together the flour, baking soda, and salt.
-
Add the chocolate mixture to the center of the flour mix, stirring just until combined.
-
Fold in the milk chocolate chips.
-
Place batter into a greased 12-cup muffin tin 2/3 full.
-
Bake 20-23 minutes or until a toothpick can be removed clean.
-
Cool for 5 minutes in the pan, then finish cooling on a wire rack.