Whisk the
butter
until it’s fluffy, alternatively you get to room temperature by letting it sit outside of the fridge for a while or by gently heating it in a microwave or waterbath.
Add the
sugar
. Then heat the
chocolate
to room temperature and add it as well.
Crack the
eggs
and seperate the yolk and eggwhite, add the yolk. Set the eggwhite aside.