Bake any muffins (for example, muffins with jam).
Melt butter or use very soft butter. Beat butter with cream cheese and powdered sugar for 2-3 minutes until fluffy.
Place mixture in refrigerator for at least half an hour.
Put topping in a freezer bag and cut off one corner. The topping will make enough for about 12 cupcakes.
Decorate the marshmallows with the food pen (see photo).
Pipe the topping on the muffins and place the marshmallows on top.