You can either use a pan ( about 1″ deep) or a better option is to use a springform pan; it just makes it so much easier to transfer it out without breaking it. If you proceed with the latter, clamp a parchment paper in the springform, and using the extra butter, coat a thin layer on the sides of the pan. Put the extra cacao in and swivel it in the pan so it sticks to the butter, this will prevent the cake from sticking. Reverse the pan to remove excess cacao and set it aside for now.

Melt the butter either in a small pot or microwave then stir in the sugar, salt, and cacao powder. Once it’s all mixed in, add the egg and make sure they are well incorporated. Add the flour and stir until you have a smooth texture and there are no more clumps. Don’t over mix.

Pour the mixture into the pan and bake at 350F* for 18 minutes. At this point, it’s not fully cooked and should wiggle a little if you shake it. That’s exactly what you want. If you leave it longer it will be more cooked ( duh) and be less moist/runny. Put it in the fridge for 90 minutes so it’s entirely cooled down.