TOPPING: Combine brown sugar, butter and flour. Mix well. Stir in nuts and 1/2 cup mini-morsels and set aside. MUFFIN: Preheat oven to 350ºF.  Combine flour, baking powder, baking soda and salt; set aside. In large bowl, combine butter, sugar and vanilla; beat until fluffy. Add eggs, one at a time, beating well after each addition. Gradually add flour alternately with sour cream. Fold in remaining 1 1/2 cups mini-morsels. Spoon into paper-lined muffin cups, about half full. Sprinkle each with 1 tablespoon topping. Bake for 20 to 25 minutes. Cool completely. Makes about 18 muffins.