Preheat oven to 375°.
Coat 4 (6-ounce) ramekins or custard cups with cooking spray, and dust each ramekin with 1 teaspoon sugar. Place on a baking sheet.
Combine chocolate, butter, and 3 tablespoons sugar in a small saucepan. Cook over low heat until melted. Add cocoa, flour, and salt, stirring with a whisk until blended. Gradually stir in milk; cook over medium heat until mixture thickens (about 3 minutes), stirring constantly. Remove from heat. Cool.
Beat egg whites with a mixer at high speed until foamy. Add remaining 3 tablespoons sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently fold one-fourth of egg white mixture into chocolate mixture; repeat procedure with remaining egg white mixture, one-fourth at a time. Spoon into prepared ramekins; sprinkle each serving with 1 teaspoon nuts. Bake at 375° for 20 minutes. Serve immediately.