Using a stand mixer or hand mixer, beat the butter and sugar for about 2 minutes until light and fluffy. Add the salt, egg, flour, vanilla, and baking powder, and mix until well combined. Then slowly fold in the chocolate.
Cover the finished dough with plastic wrap and let it rest in the refrigerator for several hours.
After resting, preheat your grill or oven to about 180°C. Place the dough in a buttered cast iron skillet and bake for about 15–20 minutes. Then place the marshmallows on top of the dough and continue baking, melting the grilling chocolate at the same time. The dough is ready when the cookies are still slightly soft and the marshmallows are toasted and melting.
Drizzle the finished cookie dough with melted grilling chocolate and caramel sauce, then serve with ice cream and whipped cream.