1 1/2 cups all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon fine sea salt
1/4 teaspoon baking powder
1/2 cup (1 stick) unsalted butter
1 cup firmly packed dark brown sugar
1 teaspoon pure vanilla extract
1 large egg, lightly beaten
1 cup semisweet chocolate chips
1/2 cup unsalted peanuts, chopped
15 caramel candies, halved (optional)
1. Preheat the oven to 350 degrees. Whisk together the flour, baking soda, salt, and baking powder in a bowl.
2. Heat the butter in a 10-inch cast-iron skillet over low heat. Add the brown sugar, stirring until dissolved.
3. Add the butter mixture to the flour mixture. Add the vanilla and egg. Fold in the chocolate chips, peanuts, and caramels.
4. Transfer the batter to the buttery skillet, smoothing the surface with a spatula. Bake until a cake tester inserted into the center comes out clean, 20 to 25 minutes. Place on a wire rack to cool. Slice while still slightly warm.