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)