Follow box instructions to mix cake batter. Add to a greased mini-cupcake pan and bake for 10-15 or until baked through. Allow to cool completely, then remove from pan.
Roll red fondant (you can buy this at most baking supply stores, or make it yourself!) until very thin but will still hold it's shape. Cut out 24 2½ inch circles out of the red fondant.
Ball up small pieces of tin foil and place each fondant circle over them, with the tin foil creating a little bump in the center. You can also add smaller ones to the outer circle to create natural looking mushroom top shapes. Allow fondant to dry until they hold their shape and then remove foil (typically overnight).
Use white royal icing (you can get this pre-made in small tubes, or make your own) to create small dots of varying sizes on top of fondant pieces and allow to dry (this typically only takes 15-20 minutes).
Pipe a small dollop of white frosting on each cupcake, then top with the fondant toppers!
