Sift together cocoa and next 3 ingredients in a medium bowl; set aside.
Beat butter and sugar at medium speed with an electric mixer until light and fluffy. Add eggs, 1 at a time, beating until well blended after each addition. Stir in vanilla.
Add cocoa mixture to butter mixture alternately with sour cream, beginning and ending with cocoa mixture. Beat at low speed until blended after each addition. Stir in morsels.
Place 12 paper baking cups in a muffin pan; spoon batter evenly into cups, filling completely full.
Bake at 350° for 25 to 30 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 5 minutes; transfer to a wire rack, and cool 30 minutes or until completely cool. Spread cupcakes evenly with White Frosting.
Also lightened a touch with 1/4 cup each butter/applesauce and used light sour cream. I didn't do frosting as it seemed it would be quite rich as-is. If made again, I'd cut down on the chocolate chips to maybe 3/4 or 1 cup. A very dense, rich, moist brownie cupcake.
These are great! Previous reviewer must have done something wrong. Somewhat dense, but moist, very chocolate-y and very rich. I would call these brownie cupcakes. I needed 14 for my son's class and got 15 out of the recipe. I almost hate to waste these on a bunch of 4 year olds!
With all of the butter in this recipe, I expected something rich. Instead, these cupcakes were dry and tasted way too much like the unsweetened chocolate. The best part was the icing. I would not make this again.