Chocolate Caramel Graham Crackers

from Gourmet Magazine January 2003

12 (4 1/4 x 2 1/2") graham crackers
1 1/2 sticks unsalted butter, cut into pieces
1/2 C packed light brown sugar
1/8 tsp salt
1 1/2 C semisweet chocolate chips (9.5oz)
1 C walnuts, pecans or almonds (3-4oz), chopped

Preheat oven to 375. Line a 15x10x1" baking pan with foil, leaving 2" overhang at each end. Line bottom of pan with graham crackers (it will be a tight fit). Melt butter in heavy saucepan over low heat, then add brown sugar and salt. Cook, whisking, until mixture is smooth and combined well, about 1 minute. Pour over crackers, spreading evenly, and bake in middle of oven until golden brown and bubbling, about 10 minutes. Scatter chocolate chips evenly over crackers and bake until chocolate is soft, about 1 minute. Remove pan from oven and gently spread chocolate evenly over crackers with offset spatula. Sprinkle nuts evenly over chocolate and cool crackers in pan on a rack 30 minutes. Freeze until chocolate is firm, 10-15 minutes. Carefully lift crackers from pan by grasping both ends of foil, then peel foil from crackers. Break crackers into serving pieces.