Melt 60g of butter using a microwave or double boiler.

Mix 1 room-temperature egg and 60g sugar together until combined.

Sift 60g cake flour, 15g cocoa powder, and 2g baking powder together, then mix into the egg and sugar mixture.

Add the melted butter to the batter and mix well.

Refrigerate the batter for 30 minutes to 1 hour.

Prepare the madeleine molds by brushing them with butter and dusting with flour. Fill each mold with batter up to 70–80% capacity.