Preheat oven to 400°F (200°C). Line muffin pan with paper liners.

In a medium sized bowl, stir together flour, baking powder and salt and set aside. In a large mixing bowl, cream butter, cocoa powder and sugar until fluffy. Add the eggs one at a time and mix well between each addition. Mix in sour cream and vanilla. Mix in half of the milk. Then mix in half of the flour mixture. Mix in the rest of the milk then the rest of the flour mixture. Stir in chocolate chips (saving a small handful for the tops of the muffins).

Fill the muffin papers to the top with batter and sprinkle with the remaining chocolate chips. This recipe makes 14 muffins; fill the empty muffin recesses half full with water in order for the muffins to bake evenly.

Bake for 5 minutes at 400°F (200°C) then reduce oven temperature to 350°F (165°C) and bake for an additional 13-15 minutes until a toothpick inserted into the middle of one muffin comes out clean (if you hit a melted chocolate chip, test again). Cool in pan on a wire rack for 10 minutes then remove from pan and cool completely on wire racks. Tightly covered, muffins will stay fresh for two days. Muffins can be frozen for up to one month.