Dark-Chocolate Brownies with Caramel and Salted Peanuts

Line the bottom of a 9-inch square baking pan with parchment paper. Butter paper and sides of pan. Place caramels, flour, and cocoa in a medium bowl and toss to combine. Set aside. In a double boiler set over simmering water, melt butter. Add chocolate and stir until melted. Remove from heat and let cool, about 10 minutes. Meanwhile, preheat oven to 350 degrees F. In a large bowl, whisk together sugars, eggs, vanilla, and salt until very thick, about 3 minutes. Stir in chocolate mixture. Stir in reserved caramel mixture and peanuts, mixing until just combined. Spread brownie batter in prepared pan. Bake for 30 minutes. Transfer to a wire rack and cool in pan. Refrigerate brownies until chilled, 3 to 4 hours, before cutting into squares.