Preheat oven to 350ºF. Line an 8-inch metal pan with foil and spray foil with cooking spray.

Combine flour, salt, brown sugar in bowl of food processor; pulse to mix. Add 4 tablespoons of the butter and pulse until mixture is coarse. Add the egg and pulse until mixed throughout. Add the nuts and pulse to mix.

Reserve 1 cups crumb mixture and press remainder firmly into pan. Bake 15 minutes.

In heavy saucepan, over low heat, melt caramels with sweetened condensed milk and remaining 2 tablespoons of butter. Pour over prepared crust. Top with reserved crumb mixture. Bake 20 minutes or until bubbly. Cool. Cut into bars. Store loosely covered at room temperature.