Preheat the oven to 350° F. Line 12 to 18 cupcake cups with paper liners.
In a large bowl, sift together the flour, cocoa powder, baking powder, baking soda and salt. In a separate bowl mix the sugar and butter until creamy. Add the eggs, then milk, and vanilla. Add to flour mixture and beat well; Add boiling water and whisk until smooth. Divide the batter evenly among 12 to 18 lined cupcake cups.
Bake for about 22 minutes, or until the cake springs back when pressed gently with your finger. Cool on a wire cooling rack.
To prepare the frosting: Beat the butter until smooth and fluffy. Add half of the powdered sugar, 1/2 cup at a time, and beat until incorporated. Add 2 tablespoons of the heavy cream and beat well on medium speed. Add the vanilla extract and 12 drops of red and 45 drops of yellow food coloring. Mix until the color is consistent, then adjust to get it the shade of orange you want. If the mixture is too stiff, add more milk until the mixture is firm and creamy.
Use a #32 star tip to pipe the frosting onto cooled cupcakes. Decorate with Halloween candy sprinkles and chocolate candy.