Preheat oven to 350°. Microwave dark chocolate morsels at HIGH 1 1/2 minutes or until melted and smooth, stirring at 30-second intervals.
Beat butter and cream cheese at medium speed with an electric mixer until creamy. Beat in sugar until light and fluffy. Add eggs, 1 at a time, beating until blended after each addition. Stir in vanilla.
Combine flour and next 3 ingredients. Gradually add to butter mixture alternately with sour cream, beating until blended. Stir melted chocolate into batter. (Batter will be very thick.) Spoon batter by rounded tablespoonfuls into lightly greased miniature muffin pans.
Bake at 350° for 11 to 13 minutes or until a wooden pick inserted in centers comes out clean. Cool in pans on wire racks 5 minutes. Remove from pans to wire racks, and cool completely (about 30 minutes). Spread cupcakes with Double Shot Latte Buttercream. Garnish, if desired.
Note: To prepare regular-size cupcakes, spoon batter into 2 lightly greased 12-cup muffin pans, filling two-thirds full. Bake at 350º for 22 to 24 minutes or until a wooden pick inserted in centers comes out clean. Cool and decorate as desired. Makes 2 dozen.