Butter cut into small cubes. I couldn't stand it at room temperature. It's already soft enough. Importantly, to not from the freezer.
Marshmallows put in 0.5 liter jar (note that double marshmallows) and 30 seconds in the microwave.
The marshmallow will increase in size. And then act very quickly: marshmallows begin to beat with a mixer, placing the oil piece by piece. After half of the oil is mixed in the marshmallow, stop the mixer, put a jar of cream in a pot of cold water and continuing to whisk, add a piece of the remaining butter in the cream.
Beat for five minutes.
The cream holds its shape well and is suitable for rinsing and decorating cakes.