Preheat oven to 350 degrees. Line the bottom and sides of a 9 x 13-inch pan with aluminum foil, allowing 2 to 3 inches to extend over sides. Spray foil with non-stick cooking spray.
Microwave chocolate and butter in a large microwave-safe bowl on HIGH for 1 1/2 to 2 minutes or until melted and smooth, stirring at 30-second intervals. Using an electric mixer, beat in 2 cups sugar. Add eggs, one at a time, beating after each addition. Add food coloring, and 1 teaspoon vanilla. Slowly add 1 1/2 cups flour and 1/8 tsp. salt, beat until just blended. Pour batter into prepared pan.
In a medium bowl, beat cream cheese and remaining 1/4 cup sugar until fluffy. Add egg whites, remaining 1 tsp. vanilla, and 1 tablespoon flour, beat until smooth. Drop cream cheese mixture by heaping tablespoonfuls over batter in pan and gently swirl with a knife.
Bake for 35 to 40 minutes or until a wooden toothpick inserted in center comes out with a few moist crumbs. Cool completely in pan on a wire rack. Lift brownies from pan, using foil sides as handles. Gently remove foil; cut brownies into squares.