1. Preheat oven to 350°. Line bottom and sides of a 9-inch square pan with aluminum foil, allowing 2 to 3 inches to extend over sides; lightly grease foil.
2. Microwave chocolate and butter in a large microwave-safe bowl at HIGH 1 1/2 to 2 minutes or until melted and smooth, stirring at 30-second intervals. Whisk in sugar. Add eggs, 1 at a time, whisking just until blended after each addition. Gently stir in flour and next 4 ingredients. Pour mixture into prepared pan.
3. Bake at 350° for 44 to 48 minutes or until a wooden pick inserted in center comes out with a few moist crumbs. Cool completely on a wire rack (about 2 hours).
4. Lift brownies from pan, using foil sides as handles; gently remove foil. Spread Small-Batch Cream Cheese Frosting on top of brownies, and cut into 16 squares. Garnish, if desired.
Line pan with foil by trimming two long foil pieces to a 9-inch width. Fit strips, crossing each other, in the pan.