All you need is:

4 eggs

1/2 cup of sugar

120g butter

1/2 cup of cocoa powder

1/2 cup of all purpose flour

tea spoon of baking powder

Mix the eggs with sugar, add melted butter and flour with baking powder and cocao powder. You should get a smooth thick texture, but still liquid. Pre-heat the over at 220° C , bake it for 5 min if you want it really liquid or 7 min if you want only the middle to be liqued ( I’ve baked it for 7 minutes)