Step 1 - Preheat oven grill on medium-high heat. Place chocolate in a small heavy-based ovenproof frying pan over medium heat. Cook for 4 minutes, stirring occasionally, or until melted.
Step 2 - Remove pan from heat and top with marshmallows. Grill for 2 minutes or until marshmallows are golden. Stand for 5 minutes before serving with biscuits.