Preheat oven to 350 degrees. Line 14-16 muffin tin slots with parchment or foil liners.
In a large bowl, beat the sugars and oil until combined, about 2-3 minutes. Add the eggs, one at a time, then the vanilla extract, Greek yogurt, and mashed banana. Mix in the flour, baking powder, baking soda, cinnamon, cloves, and salt. Do not overmix.
Scoop the batter into the prepared muffin tins, filling 2/3 of the way to the top. Bake for 22-25 minutes until the centers are set and an inserted toothpick emerges clean. Cool 5 minutes in the pans, then move to a wire rack. Cool completely.
In a microwave-safe bowl, heat the milk chocolate for 1 minute. Stir until the bowl is no longer warm, then microwave 30 seconds, if needed, until completely smooth. Let cool 5 minutes.
In a large bowl, beat the butter, powdered sugar, cocoa powder, vanilla, and heavy cream on high speed until fluffy. With the mixer running, stream in the milk chocolate, whipping until combined.
Pipe or frost the buttercream onto each cupcake. Decorate with 2-3 Cadbury mini eggs, any color you wish!