Melt the chocolate in a steam bath.
Put the marshmallows in the microwave for a few seconds until soft.
Then we add the chocolate to the marshmallows and mix well, then the cream and melted butter. Stir until smooth.
Add the icing sugar and knead well, it is better to do this with a mixer with a nozzle for the dough. Then we roll out the finished chocolate mastic and decorate the cake.