Ingredients

  • 1/2 cup (1 stick) unsalted butter, room temperature, plus more for pan
  • 2 1/4 cups all-purpose flour
  • 2 1/4 teaspoons baking powder
  • 1 teaspoon coarse salt
  • 1 1/2 cups packed dark-brown sugar
  • 3 large eggs
  • 1 teaspoon pure vanilla extract
  • 1 cup miniature marshmallows
  • 1 cup semisweet chocolate, coarsely chopped
  • 1 cup white chocolate, coarsely chopped
  • 1 cup butterscotch chips
  • 18 soft caramel-candy cubes, coarsely chopped

Method

  • Preheat oven to 350 degrees. Lightly butter a 9-by-13-inch baking pan. Line with parchment paper, allowing a 2-inch overhang on the longer sides. Brush parchment with butter (not overhang).
  • Whisk together flour, baking powder, and salt in a medium bowl. In the bowl of an electric mixer fitted with the paddle attachment, mix butter and brown sugar until fluffy, about 2 minutes. Add eggs and vanilla; mix until well combined. Mix in flour mixture until combined. Fold in half of each of the marshmallows, chocolates, butterscotch chips, and caramels.
  • Spread batter in prepared pan. Scatter remaining marshmallows, chocolates, butterscotch chips, and caramels on top. Bake until top is golden brown and a cake tester inserted into the center comes out clean, about 35 minutes. Let cool on a wire rack. Lift out of pan, and transfer to a baking sheet. Refrigerate until set, at least 30 minutes. (Be sure to chill these, they will not slice clean if they are warm.)
  • Remove parchment, and cut into about 16 triangles. Bars can be stored in an airtight container at room temperature up to 1 week.