Sticky Peanut Cookie Bars

1. 1
   Heat the oven to 350°F and arrange a rack in the middle. Butter an 8-by-8-inch glass baking dish and set aside. Combine peanuts, flour, sugar, and salt in the bowl of a food processor. Pulse until peanuts are ground and mixture is well combined. Add butter and pulse again until mixture resembles coarse meal.
2. 2
   Press mixture evenly into the prepared baking dish and prick it all over with a fork. Bake until lightly golden, about 30 minutes. Remove from the oven and place on a wire rack.

For the topping:

1. 1
   Combine sugar, 1/2 teaspoon of the salt, and water in a medium saucepan. Bring to a boil over medium heat, stirring often until sugar is completely dissolved. Continue to boil mixture, swirling the pan occasionally (but not stirring), until it turns a deep caramel color, about 8 minutes. Remove the pan from heat and carefully stir in cream and vanilla extract (mixture will bubble up and steam).
2. 2
   Sprinkle chopped chocolate evenly over cooled peanut shortbread.
3. 3
   Stir peanuts into caramel mixture and immediately pour over shortbread and chocolate base. Sprinkle remaining 1/2 teaspoon salt over peanut bars and allow to finish cooling. Cut into rectangles and serve.