Preheat oven to 350.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, 1 3/4 c sugar, cocoa, baking powder, and salt in a large bowl, stirring well with a whisk. Place butter and chocolate in a microwave safe bowl; microwave at high for 45 seconds or until melted, stirring once. Combine milk, 1/2 t vanilla, and eggs, stirring well with a whisk. Add chocolate mixture and milk mixture to flour mixture; beat with a mixer at medium speed until blended. Spoon batter evenly into 13 x 9 baking pan coated with cooking spray.
Place remaining 1/4 c sugar, remaining 1/4 t vanilla, cheese, and egg white in a medium bowl; beat at medium speed until well blended using clean, dry beaters. Drizzle cheese mixture evenly over chocolate mixture; swirl batters together using the tip of a knife. Bake at 350 for 30 minutes or until batter begins to pull away from sides of pan. Cool completely on a wire rack.
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