This moon is definitely not made of green cheese! In fact, it's a very kid-friendly baking project. Your little assistant will love crushing the cookies, mixing them into the frosting, and helping create the moon's surface (which needn't be smooth or neat). If you use chocolate cake, any crumbs that end up in the frosting will blend right in!
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Heat the oven to 350 degrees. Divide the prepared batter into 2 equal parts. Pour one half into a greased 2 1/2-quart oven-safe bowl and the other into a greased 9-inch round pan. Bake both until a toothpick inserted in the centers comes out clean, approximately 40 minutes for the bowl and 25 minutes for the pan. Let the cakes cool thoroughly, then remove them from the bowl and pan.
Using a rolling pin, crush the chocolate cookies in a Ziploc bag (leave a small opening for air to escape). Empty the can of frosting into a bowl, then stir in the crumbs.
Frost the top of the flat cake, then place the dome cake on it. (If necessary, first trim the bottom of the dome with a large knife so that it's level.) Frost the rest of the cake.
Push the Necco wafers into the frosting to form craters on the moon's surface. Add the astronauts and the flag.