Preheat the oven to 350°F. In a large mixing bowl, cream together the butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Stir in vanilla extract. In another bowl, whisk together flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, alternating with milk. Mix until just combined.

Line a cupcake pan with paper liners. Pour the batter evenly into the liners, filling each about two-thirds full. Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat the softened butter until creamy. Gradually add powdered sugar, beating until smooth. Add milk and vanilla extract, and continue to beat until fluffy. Divide the frosting into separate bowls and add food coloring to each to achieve desired colors.

Using a piping bag, frost the cooled cupcakes with colored frosting in swirls or peaks. Add candies and sprinkles for decoration, creating spooky designs that fit your Halloween theme.

Arrange the decorated cupcakes on a serving platter. Serve at room temperature for best flavor and texture.

Place any leftover cupcakes in an airtight container. Store at room temperature for up to 3 days or refrigerate for up to a week. Bring to room temperature before serving for best taste.