1. Preheat oven to 350°.
2. Beat butter and sugar at medium speed with an electric mixer until creamy. Add eggs, 1 at a time, beating until blended after each addition.
3. Combine flour, baking powder, and salt; add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in vanilla.
4. Place paper baking cups in 2 (12-cup) muffin pans, and coat with cooking spray; spoon batter into cups, filling two-thirds full.
5. Bake for 12-15 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans to wire racks, and cool completely.
Pecan Pie Frosting:
1. Whisk together first 6 ingredients in a heavy saucepan. Bring to a boil over medium heat, whisking constantly. Boil, whisking constantly, 1 minute or until thickened.
2. Remove pan from heat; stir in butter and vanilla, whisking until butter melts. Place a sheet of plastic wrap directly on surface of mixture (to prevent a film from forming); chill about 3 hours or until thick. Makes 4 cups. Frost each cupcake.
1. Unroll piecrust on a flat surface. Using a 1/2-inch cookie cutter, cut out leaves. Bake according to package directions. Makes about 48 leaves.
Top each cupcake with toasted pecans and 1 piecrust leaf.