Preheat your oven to 350 degrees. First, we'll prepare the butter. Cut your butter into about tablespoon-sided pats and place in a glass bowl. You'll want to partially melt the butter and you have a couple options to do this. Simply place in the microwave to start with 25 seconds, or put the bowl over a little bit of simmering water inside a sauce pan, and that will do the trick too. Your melted butter should have some partial solids in there. Most will be liquid, but you'll be able to see pats that are soft and not liquid. In a separate bowl, place the graham crackers and sugar. Combine the two.
Pour the butter over the dry mixture.
Combine with a spoon.
Pour into the bottom of a prepared pan. Otherwise, if you're making smaller desserts, like mini cupcakes or cheesecakes, use a teaspoon-sized amount for each holder.
Use your finger tips to gently press the crust down.
Place in the oven for 6 minutes - The crust will bake evenly. Remove from oven.
Pour your main batter over the prepared graham cracker crust bottom. This is Key Lime cake. It can be cake batter, cheesecake batter or brownie batter - anything that will go back into your oven to bake.
You'll bake that batter for almost whatever time your main recipe calls for. Because the graham cracker crust bottom takes up some space - especially with smaller desserts - you'll want to remove them from the oven a miniute or so beforehand. Just check to be sure the center is baked-through before removing from the oven.