1Heat oven to 350°F (325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan with shortening or cooking spray. Make brownie batter as directed on brownie mix box for cakelike brownies. Spread batter in pan. Bake 26 to 30 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean.
2Meanwhile, in large bowl, mix filling ingredients. Remove brownies from oven. Carefully spoon and spread filling evenly over brownies. Bake 15 minutes longer (filling will not brown). Cool completely, about 1 1/2 hours.
3In small microwavable bowl, microwave chocolate chips and 1/2 teaspoon oil on High 30 to 40 seconds, stirring every 10 seconds, until chips are melted. Spoon into resealable food-storage plastic bag; seal bag. Cut small tip from corner of bag; drizzle chocolate over filling. For bars, cut 8 rows by 6 rows.