Melt butter completely in a saucepan and add the chocolate. Let it melt on low heat so it doesn't burn.
Separate the eggs into two bowls. Add 25-50 grams of sugar to each bowl depending on desired sweetness.
Using an electric mixer, whisk the egg whites until stiff peaks form, adding sugar gradually. Whisk the egg yolks in the other bowl with sugar as well (around 3-4 minutes each).
Fold the whipped egg yolks into the whites (barely mixed together) and add the melted chocolate and butter mixture into the mixture.
When the mixture is completely homogeneous, keep it in the bowl or add it to a preferred serving dish.
Let it sit in the fridge for at least 4-5 hours, best overnight.
