1. Place the chocolate in a microwave-safe plastic bowl. Heat in the microwave in 30 second increments, stirring after each addition of heat, until completely melted.
2. Place the cream into a saucepan and bring to the boil.
3. Add the marshmallows and butter to the hot cream and stir over low heat until completely melted and combined.
4. Remove from the heat and add to the melted chocolate, mix to incorporate.

NOTES:

• The sauce is best enjoyed on the day it is made but can be stored in an airtight container in the refrigerator for up to 7 days.
• To avoid burning the chocolate, the sauce can be reheated or kept warm over a very low heat.