Banana Fudge-Walnut Brownies
["3/4 c. all-purpose flour", "1/2 c. sugar", "1/3 c. chopped walnuts", "1/3 c. mashed, ripe bananas", "1/2 tsp. vanilla", "1/4 tsp. baking powder", "1/4 tsp. salt", "1 egg", "1/4 c. (1/2 stick) margarine or butter", "1 (6 oz.) pkg. semi-sweet chocolate chips"]
["Heat oven to 350\u00b0.", "Grease bottom only of an 8-inch square pan."]
["all-purpose", "sugar", "walnuts", "bananas", "vanilla", "baking powder", "salt", "egg", "margarine", "semi-sweet chocolate chips"]