Chocolate-Marshmallow Ribbon Cake

Heat oven to 375°F. Line 15x10x1-inch pan with foil; grease generously. In large bowl, mix flour, cocoa, baking powder and salt; set aside.

In small bowl, beat eggs with electric mixer on high speed about 3 minutes or until very thick and lemon colored. In large bowl, gradually beat 1 cup granulated sugar into eggs. On low speed, beat in 1/3 cup water and the vanilla. On low speed, beat in flour mixture just until batter is smooth. Pour into pan, spreading batter to corners.

Bake 12 to 15 minutes or until top springs back when touched lightly. Generously sprinkle clean towel with powdered sugar. Run knife around side of pan to loosen cake; turn upside down onto towel. Carefully remove foil. Cool cake completely, about 30 minutes.

In 3-quart saucepan, mix egg whites, 1 1/2 cups granulated sugar, the cream of tartar, corn syrup and 1/3 cup water. Cook over low heat, beating with electric mixer on high speed until stiff peaks form and scraping bottom and side of saucepan occasionally. Remove from heat. Add marshmallows; beat until smooth.

Cut cake crosswise into four 10x3 3/4-inch rectangles. Layer rectangles, spreading each with about 1 cup frosting. Spread top with remaining frosting.

In 1-quart saucepan, heat chocolate and butter over low heat, stirring occasionally, until melted; remove from heat. Stir in powdered sugar and 5 teaspoons water until smooth. Stir in additional boiling water, 1/2 teaspoon at a time, until desired consistency. Pour glaze over cake, allowing some to drizzle down sides.