Mississippi Mud Bars
["3/4 packed brown sugar", "1/2 butter softened", "1 egg", "1 tsp. vanilla", "1/2 tsp. baking soda", "1/4 tsp. salt", "1 cup plus 2 tbsp. all purpose flour", "1 cup (6 oz) semisweet chocolate chips divided", "1 cup (6 oz) white chocolate chips divided", "1/2 cup chopped walnuts or pecans"]
["Preheat oven to 375 degrees.", "Line a 9 inch square pan with foil; grease foil.", "Beat sugar and butter in large bowl until blended and smooth.", "Beat in egg and vanilla until light.", "Blend in baking soda and salt.", "Add flour, mixing until well blended.", "Stir in 3/4 cup each semisweet and white chocolate chips and nuts. Spread dough in prepared pan.", "Bake 23 to 25 minutes or until center feels firm.", "DO NOT OVER BAKE."]
["brown sugar", "butter", "egg", "vanilla", "baking soda", "salt", "flour", "chocolate chips", "white chocolate chips", "walnuts"]