Yes! You can bake the brownies ahead, cut them as directed, then freeze them wrapped tightly in plastic wrap. You can also freeze them uncut, just be sure to thaw them about halfway before you cut them. Then make the frosting and decorate. You can also freeze these fully decorated or store them in the fridge for 2-3 days. However, the frosting will lose some of its fluffy texture. You will also need to store them in a flat layer, which can take a lot of space.