Mug cakes are usually single-serving, so you have 1 egg, 1 banana (or equivalent amount of puree, I use pumpkin), any flavoring or spices (chocolate, cinnamon etc.) as desired, maybe 1-2 tbsp of "primal flour" (coconut or almond) OR nut butter (have used almond butter with success). Mix it all up in a mug, microwave for 2.5 minutes, add 30 sec increments as needed to cook the center (so it's not shiny anymore), or give up and eat it anyway. It'll be hot! I don't ever grease the mug and it cleans up easily, but if you do, you could probably dump the thing out of the mug. Don't know why you'd want to, it's more fun that way. I add a little honey or maple syrup because pumpkin puree isn't sweet on its own.