Preheat oven to 200°C and grease a 12-hole mini-muffin pan. Process butter, caster sugar, banana, eggs and vanilla in a food processor until well combined. Place flour, coconut and chocolate in a large bowl, then fold in banana mixture. Working in batches, place dessertspoons of mixture into pan. Bake for 15 minutes or until risen and golden. Cool slightly in pan, then turn out onto a rack to cool completely. Repeat with remaining batter. Serve dusted with icing sugar.