Preheat oven to 350 degrees F. Line twenty-four 2-1/2-inch muffin cups with paper bake cups.
In large mixing bowl beat butter with electric mixer on medium-high for about 1 minute. Add sugar. Beat until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Whisk together flour, baking powder, soda, and salt. Add flour mixture in two additions, alternating with buttermilk, and beating on low after each addition until combined.
Fill lined muffin cups about 2/3 full. Bake 15 to 18 minutes or until a toothpick inserted in center comes out clean. Cool in pans on wire rack for 5 minutes. Remove cupcakes from pan; cool completely on wire rack.
Fill and/or frost as directed, below. Pour nonpareils into a shallow dish. After frosting, roll edge of cupcakes in nonpareils to make colored rim, using your hands to help nonpareils stick to frosting if needed. For toppers, place 4 oz. semisweet chocolate in small microwave-safe bowl. Cook in the microwave for 2 minutes, stirring every 30 seconds until melted. Dip small crackers such as Wheat Thins in melted chocolate. Immediately place on tip of chocolate-covered cherry, and top with mini M&M and fruit leather cut to resemble a tassel. Place cupcakes in covered container and refrigerate until set or up to 3 days. Makes 24 cupcakes.
Sour Cream Frosting
Allow butter to stand at room temperature for 30 minutes. In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Beat in sour cream and vanilla. Gradually add powdered sugar, beating well. Beat in enough of the milk to make frosting piping consistency.