Mix the rice flour, flaxseed meal, sugar, cocoa, baking powder, baking soda, and salt together in a bowl.
Place the peeled and sliced avocado, egg, vanilla, milk and dark chocolate in the bowl, and using a handheld electric mixer, beat the wet and dry ingredients up well.
Then spoon mix into a lined muffin/cupcake tray.
Bake for 12-15 minutes.
Let cool.
Make the frosting by melting the dark chocolate - I melted mine by placing the dark chocolate chips in a microwave safe bowl and microwaving for 25 seconds, removing from microwave, stirring and returning back to microwave for another 25 seconds.