Butterscotch Milk Chocolate Bars
["1 1/2 c. packed brown sugar", "1/2 c. softened margarine", "2 tsp. vanilla", "2 eggs", "2 c. plain flour", "2 tsp. baking powder", "1/2 tsp. salt", "11.5 oz. pkg. milk chocolate chips", "1/2 c. nuts (optional)"]
["Preheat oven to 350\u00b0.", "Grease 13 x 9-inch pan.", "In large bowl, beat brown sugar and margarine until light and fluffy.", "Add vanilla and eggs, mix well.", "Add flour, baking powder and salt; mix well. Reserve 1 cup chocolate chips for frosting.", "Stir in remaining chips and nuts.", "Bake 15 to 20 minutes.", "Cool completely and frost."]
["brown sugar", "margarine", "vanilla", "eggs", "flour", "baking powder", "salt", "milk chocolate chips", "nuts"]