1. Preheat oven to 350°. Beat butter and cream cheese at medium speed with an electric mixer until creamy. Beat in sugars until light and fluffy. Add eggs, 1 at 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 tablespoonfuls into lightly greased miniature muffin pans.
3. Bake at 350° for 13 to 15 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).
4. Microwave semisweet chocolate and 1/4 cup whipping cream in a microwave-safe bowl at HIGH 1 minute, stirring at 30-second intervals. Whisk in 2 Tbsp. whipping cream until smooth. Dip tops of cupcakes in chocolate mixture, and let stand until chocolate is set (about 30 minutes). Pipe or spread Salted Caramel Buttercream onto cupcakes. Garnish, if desired.
Note: We tested with Artisan Salt Company Cyprus Mediterranean Flake Salt.
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.