Beat the egg whites until stiff but still soft. Optional: Add 3 tablespoons of sugar slowly while the egg whites are beating. Set aside.
Melt the chocolate chips either using a microwave; 30 seconds at a time and mix, repeat until the melted chocolate is smooth with no lumps. Or, over the stove on a very low heat.
Add the egg yolks one at a time to the melted chocolate and mix well until they are all combined.
Add 1 cup of egg whites to the melted chocolate and fold until combined.
Transfer the chocolate mixture to the egg whites bowl and fold the two together, that might take a minute or two. Take your time, make sure the mixture does not have spots of egg white beater.
Transfer to a cake pan (lined with parchment paper for easy clean up) and bake at 325 for 20 minutes. Let cool and garnish with powder sugar before serving.
