Mix the butter with the sugar until creamy, then stir in the egg. Mix the oat flakes with the flour, desiccated coconut and baking powder and stir in. Cover and chill the dough for about 2 hours.
Preheat the oven to 175 ° C, line two baking sheets with parchment paper. Mix the brown sugar and desiccated coconut.
Shape the dough into small balls, then press them into the sugar-coconut shavings mixture. Place on the baking sheets and bake one after the other on the middle rack in the oven for about 15 minutes. Let cool down on the baking sheet.