Melt the butter over medium-low heat.
Save about a tablespoon melted butter, to butter the muffin tray.
Break the chocolates into pieces.
Remove the butter from heat once melted and add the chocolate and mix until no particles are left. Set aside to cool.
In a separate bowl break the eggs, add the sugar, mix for 3 minutes.
After the three minutes, gradually add the flour while continuing to mix.
Also, add the chocolate mixture and mix for another 3-4 minutes.
Meanwhile butter the muffin tray, including the sides. Sprinkle with cocoa.
Fill the muffin tray holes halfway with the cake mixture.
Bake in a preheated oven at 200° Celsius for 7 minutes.
Take out of the oven.
Flip over onto serving plates.
Sprinkle with powdered sugar.
Serve immediately.