At 30 second intervals, melt chocolate chips with coconut oil. Stir until smooth. You'll only have to do this for about a minute.
Spoon chocolate into silicone or paper cupcake liners (paper is fine, but silicone is so much easier to peel when you're done). I used about 1 tsp per cup, maybe a titch more. Use the back of a spoon to gently press the chocolate up the sides of the liners. Ensure that the bottom is even. Repeat with all 12 liners, then let set in the freezer.
Meanwhile, combine coconut butter, icing sugar, coconut flour, and butter to make the filling. Spoon about 2 tsp of the mixture into the chilled chocolate cups until all the filling is evenly distributed. Use your fingers or the back of a spoon to press the filling down evenly. Coat with about 1/2 tsp of chocolate (you'll use the remaining melted chocolate) and set in the freezer for about 10 minutes.
Once set, pop them out of the cupcake liners and enjoy!