2 cups all-purpose flour
2/3 cup unsweetened cocoa powder
1 1/4 teaspoons baking soda
1 teaspoon salt
1/4 teaspoon baking powder
3/4 cup butter, softened
1 2/3 cups granulated sugar
3 large eggs
1 teaspoon vanilla extract
1 1/3 cups water
1 cup milk chocolate chips
1 cup white chocolate chips
Preheat oven to 350°F (175°C). Line medium muffin cups with paper baking cups.
In a medium bowl, combine flour, cocoa, baking soda, salt and baking powder; set aside.
Combine butter, sugar, eggs and vanilla in a large bowl and beat on high speed of electric mixer for 3 minutes. Add flour mixture alternately with water, beating just until blended.
Fold in milk chocolate chips and white chocolate chips. Spoon batter into prepared muffin cups, about 2/3 full.
Bake for 20 minutes or until top springs back when touched lightly in center. Remove from muffin cups and transfer to wire rack. Cool completely.