Preheat your oven to 400°F.
In a skillet, arrange the mini peanut butter cups evenly.
If you're using it, break the chocolate bar into pieces and scatter them over the peanut butter cups.
Next, layer the marshmallows on top.
Place the skillet in the oven and bake for 5-7 minutes until the marshmallows are golden and gooey.
For an extra golden touch, turn on the broiler for about 1 minute.
Once done, serve your delicious skillet s'mores with graham crackers for dipping and enjoy the gooey goodness!