4.5 ounces all-purpose flour (1 cup)
1/2 cup unsweetened cocoa
1/4 teaspoon salt
1/3 cup butter
2 ounces dark chocolate, chopped
1 cup granulated sugar
1/4 cup 1% low-fat milk
1 teaspoon vanilla extract
2 large egg yolks
1 large egg
Cooking spray

4 5 ounces all-purpose flour (1 cup) 1/2 cup unsweetened cocoa 1/4 teaspoon salt 1/3 cup butter 2 ounces dark chocolate, chopped 1 cup granulated sugar 1/4 cup 1% low-fat milk 1 teaspoon vanilla extract 2 large egg yolks 1 large egg

Preheat oven to 350°.
Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, cocoa, and salt in a medium bowl; stir with a whisk.
Place butter and chocolate in a medium microwave-safe bowl, and microwave at HIGH for 45 seconds, stirring every 15 seconds. Stir until smooth, and set aside. Cool slightly. Add 1 cup sugar, milk, 1 teaspoon vanilla extract, egg yolks, and egg; stir with a whisk to combine. Add butter mixture to flour mixture, stirring just until combined. Pour batter into an 8-inch square metal baking pan coated with cooking spray. Bake at 350° for 20 minutes or until a wooden pick inserted in center comes out almost clean.