Preheat oven to 350°F. Coat six 1-cup mini fluted tube cake molds with nonstick cooking spray for baking.
In a medium bowl, combine flour, baking powder, baking soda, and salt; set aside.
In a large bowl, beat 1/2 cup butter with an electric mixer on medium to high speed for 30 seconds. Add sugar and beat until fluffy. Beat in eggs, one at a time. Beat in vanilla. Beat in flour mixture alternately with sour cream, beating on low after each addition just until moistened. Fold in 1 cup chocolate chips. Divide into prepared molds.
Bake for 20 minutes or until a wooden pick inserted near the centers comes out clean. Remove and cool in a pan on a wire rack for 5 minutes. Remove from molds. Cool completely.
In a small saucepan over low heat, melt the remaining baking chips with 3 tablespoons butter until smooth and glossy. Cool slightly and spoon over cooled cakes. Sprinkle with mini baking chips.
Tip: If you don't have mini Bundt molds, coat fifteen 2 1/2-inch muffin cups with nonstick cooking spray. Fill each cup two-thirds full. Bake 13 to 15 minutes or until a toothpick inserted near the centers comes out clean. Cool 2 minutes in cups; remove and cool completely. Glaze as above.
Test Kitchen Tip: For easy glazing, transfer cooled glaze mixture to a zip-top bag. Seal and snip one corner of the bag. Glaze as above.