Mix the softened butter with sugar for about 2 minutes until light and creamy.
Add salt, egg, flour, vanilla, and baking powder, then mix briefly but thoroughly.
Finally, fold in the chocolate pieces or chips.
Cover the dough with plastic wrap and let it rest in the refrigerator for several hours (preferably overnight).
Preheat the grill or oven to 180°C (grill: indirect heat, lid closed). Butter a cast iron skillet (24–26 cm diameter).
Press the dough evenly into the pan, all the way to the edge. Bake for 15–20 minutes, until the edges are set and the center is still soft.
Remove the pan briefly and arrange the marshmallows close together on top. Return to the grill or oven; at the same time, melt the grilling chocolate. Bake until the marshmallows are toasted and the cookie is still soft (depending on heat, 3–6 minutes; optionally use the broil function briefly).
Coat with melted chocolate and caramel sauce.
Serve immediately with ice cream and whipped cream – best enjoyed warm, straight from the pan.
- Do not bake with a topping - a skillet cookie should stay gooey inside.
- If you like, sprinkle sea salt flakes on top before serving.
- Safety: The pan is extremely hot - use oven mitts!