Crunch Bars

Preparation

1. For cookie base:

   Step 1

   Arrange a rack in middle of oven; preheat to 375°F. 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.

   Step 2

   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).

   Step 3

   Scrape dough into prepared dish. Using your fingertips, spread into a thin, even layer.

   Step 4

   Bake cookie base until it is golden brown and has begun to puff and crack, about 22 minutes. DO AHEAD: Base can be made 2 days ahead. Let cool completely and store airtight at room temperature.

2. For topping:

   Step 5

   Preheat oven to 375°F. 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.

   Step 6

   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.

   Step 7

   Carefully remove foil from cookie and slide onto a cutting board. Cut into bars. DO AHEAD: Crunch Bars can be made 5 days ahead. Store airtight at room temperature.