Combine first 3 ingredients, stirring until smooth.
Melt butter in a small, heavy saucepan over medium heat. Add flour; cook 1 minute, stirring constantly with a whisk. Gradually add milk, 1/4 cup sugar, and salt; cook 3 minutes or until thick, stirring constantly. Remove from heat; stir in cocoa mixture. Spoon into a large bowl; cool slightly.
Beat egg whites at high speed of a mixer until foamy. Add 3 tablespoons sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently fold 1 cup egg white mixture into cocoa mixture; gently fold in remaining egg white mixture. Spoon into a 1 1/2-quart soufflé dish coated with cooking spray.
Bake at 375° for 45 minutes or until puffy and set. Serve warm with Raspberry Sauce.