Allow butter and eggs to stand at room temperature for 30 minutes. Meanwhile, line twenty-four to twenty-six 2 1/2-inch muffin cups with paper bake cups. In a medium bowl stir together flour, cocoa powder, baking powder, and salt. Set aside.
Preheat oven to 350 degrees F. In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Gradually add sugar, beating on medium speed until well mixed. Scrape sides of bowl. Beat for 2 minutes more. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Alternately add flour mixture and milk to butter mixture, beating on low speed after each addition just until combined.
Spoon batter into prepared muffin cups, filling each about three-fouths full. Place a candy half on top of batter in each cup.
Bake for 16 to 18 minutes or until tops spring back when lightly touched. Cool cupcakes in muffin cups on wire racks for 5 minutes. Remove cupcakes from muffin cups. Cool completely on wire racks.
To serve, remove paper liners from cupcakes. Spread cupcakes with Ganache; sprinkle with pecans. If desired, drizzle with caramel ice cream topping.