Preheat the oven to 350 degrees. Grease a 9-by-13-inch baking dish with butter.

Make the cookie layer: Place the flour, butter, and brown sugar into a mixing bowl. Mix with your hands until it forms a sandy dough. Place this mixture onto the bottom of the baking dish and spread into an even layer. Sprinkle the walnut pieces over the dough evenly and set aside.

Make the caramel: Heat 1 cup of butter and ⅔ cup brown sugar in a small saucepan over medium heat. Cook the mixture until it bubbles, about 6 to 8 minutes. Continue to cook for another 3 minutes, stirring often, until the mixture thickens and is a caramel color. Pour the caramel evenly over the walnuts in the baking dish. Transfer the baking dish into the oven and bake for about 18 minutes, until the cookie layer is cooked through.

Remove the baking dish from the oven. Sprinkle the chocolate chips on top. The chocolate will melt.Using an off-set spatula or butter knife, spread it into an even layer. Let cool. Cut into 1 ½ to 2 inch squares and serve or wrap well and keep in the freezer.