Zebras
["1 1/2 c. (9 oz.) semi-sweet chocolate chips", "2 c. all-purpose flour", "1 tsp. baking powder", "2 sticks (1 c.) butter or margarine (at room temperature)", "1 c. packed light brown sugar", "2 large eggs (at room temperature)", "1 tsp. vanilla extract", "3/4 c. walnuts, coarsely chopped"]
["Heat oven to 350\u00b0.", "Grease a 13 x 9-inch baking pan.", "Line with foil.", "Grease foil.", "Melt 1 cup chocolate chips in a small saucepan over low heat, stirring often.", "Remove from heat and cool slightly. Mix flour and baking powder."]
["semi-sweet chocolate chips", "flour", "baking powder", "butter", "brown sugar", "eggs", "vanilla extract", "walnuts"]