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["Arrange a rack in middle of oven; preheat to 375u00b0F. Line the bottom and sides of a 13x9x2"" metal or glass baking dish with foil, allowing 2"" overhang on either side; butter foil in dish.", "Using an electric mixer at medium speed, beat 1 cup butter in a large bowl until smooth, about 3 minutes. Add both sugars and salt; continue to beat until mixture is light and creamy, about 3 minutes longer. Beat in vanilla, then slowly mix in flour, beating until entirely incorporated (dough will be wet and sticky).", "Scrape dough into prepared dish. Using your fingertips, spread into a thin, even layer.", "Bake cookie base until it is golden brown and has begun to puff and crack, about 22 minutes. DO AHEAD:", "Preheat oven to 375u00b0F. Scatter chopped chocolate evenly over cookie base and bake just until chocolate is soft and has begun to melt, about 2 minutes. Immediately spread chocolate in an even layer over base.", "Scatter toppings over warm chocolate; lightly but firmly press into chocolate. Sprinkle with salt. Let cool in dish on a wire rack for 15 minutes. Using foil overhang, lift cookie from dish. Place on rack; let cool until chocolate is set, about 2 hours.", "Carefully remove foil from cookie and slide onto a cutting board. Cut into bars. DO AHEAD:"]
