Such a mass will not work if, for example, the egg is cold. The butter will simply solidify and go lumpy.
Next, add milk at room temperature, flour and baking powder.
You can take 110 grams of any flour, or 90 grams of flour and 20 grams of cocoa powder.
If you choose not to add cocoa, you can add vanilla to the batter to make the cupcakes fragrant.