To make the chocolate layers, melt the coconut oil over low heat in a small pot. Once it’s melted, remove from the stove and add the peanut butter, maple syrup, cocoa powder, and vanilla. Whisk until smooth. Divide half of this chocolate mixture into 12 silicone muffin cups (about 1 tbs each). If it seems too solid to distribute, add a little more coconut oil. Set aside the other half of the chocolate mixture to use later.
To make the peanut butter filling, melt the coconut oil in a small pot. Add the peanut butter, maple syrup, and vanilla, and whisk until smooth. Pour a generous tablespoon of this peanut butter mixture into the center of each muffin cup. Then cover each one with the remaining chocolate mixture. (Note: If the chocolate mixture is too thick to spread evenly at this point, add a little more melted coconut oil.)
Freeze the peanut butter cups for 30 minutes. Remove them from the muffin cups and store in an airtight container in the fridge or freezer. (I prefer the slightly softer texture they get when they’re stored in the fridge, but the freezer works too if you want them to be completely solid.)