1. Preheat oven to 350. Beat butter and cream cheese at medium speed with an electric mixer until creamy. Beat in sugar until light and fluffy. Add eggs, 1 a a time, beating until blended after each addition. Stir in vanilla.
2. Combine flour and next 3 ingredients. Gradually add to butter mixture alternately with sour cream, beating until blended. Spoon batter by rounded tablespoons into lightly greased miniature muffin pans.
3. Bake at 350 for 13 to 15 minutes or until a wooden pick inserted in centers racks 5 minutes. Remove from pans to wire racks, and cool completely (about 30 minutes). Spread cupcakes with desired buttercream, or dip in glaze.
NOTE: To prepare regula-sizedcupcakes, spoon batter into 2 lightly greased 12-cup muffin pans, filling two thirds full. Bake at 350 for 22 to 24 minutes or until a wooden pick comes out clean. Makes 2 dozen.