How to Make It
Preheat the oven to 350 degrees. Melt butter in an 8-inch cast iron skillet over medium-low heat. Stir in sugars and vanilla. Remove from heat and allow pan to cool about 5 minutes.
Carefully whisk eggs into the sugar mixture.
In a small bowl, combine the flour, cocoa powder, baking soda, and salt. Add the dry mixture to the skillet until just combined. Fold in peanut butter cups or chips.
Bake for 15-18 minutes, or until beginning to turn golden on top and around the edges but still soft in the center. Don’t overbake. Remove from the oven and let cool for 5 minutes.
Sprinkle with extra peanut butter cups and drizzle with chocolate syrup and melted peanut butter. Top with scoops of vanilla ice cream and serve immediately.