Preheat oven to 350°F / 180°C. Generously brush melted butter in the mini muffin wells of a mini muffin pan.
Place the almonds in a food processor, if using whole almonds, and process till they’re chopped very finely (like coarse sand).
Add the icing sugar, brown sugar, and cocoa powder and pulse a few times, until the dry ingredients have mixed well. (Alternatively, you can mix all the ingredients in a bowl using a whisk - just make sure there are no lumps).
Transfer the dry ingredients to a bowl. Add the lightly beaten egg whites and using a spatula mix this through the dry ingredients. Add the vanilla and melted butter and fold through the batter until mixed through.
Using a spoon or mini scoop to fill each mini muffin well, almost to the top - leaving some room for them to rise.
Bake in a preheated oven for 9-10 minutes, until the edges look a little crisp, the middle is slightly risen, but looks fudgy.
Let it cool completely and pop them out of the muffin pan. While the brownie bites are cooling, make the Chocolate glaze.