Marble Chiffon Cake

7 eggs, separated
2 ounces unsweetened chocolate
1-3/4 cups sugar, divided
1/4 cup hot water
2 cups all-purpose flour
2 teaspoons baking powder
1 teaspoon salt
1/4 teaspoon baking soda
3/4 cup water
1/2 cup canola oil
2 teaspoons vanilla extract
1/2 teaspoon cream of tartar

Frosting:
4 ounces semisweet chocolate
1 tablespoon butter
7 tablespoons heavy whipping cream
1 teaspoon vanilla extract
1-1/2 cups confectioners' sugar

Let eggs stand at room temperature for 30 minutes. In a small saucepan, melt unsweetened chocolate over low heat. Add 1/4 cup sugar and hot water; mix well and set aside.

In a large bowl, combine the flour, baking powder, salt, baking soda and remaining sugar. Whisk together the egg yolks, water, oil and vanilla; add to flour mixture and beat until moistened. Beat for 3 minutes on medium speed; set aside.

In another large bowl and with clean beaters, beat egg whites and cream of tartar on high speed until stiff peaks form. Fold a fourth of egg whites into the batter, then fold in remaining whites. Divide batter in half; gradually fold chocolate mixture into one portion.

Alternately spoon the plain and chocolate batters into an ungreased 10-in. tube pan. Swirl with a knife. Bake on the lowest rack at 325° for 60-65 minutes or until top springs back when lightly touched. Immediately invert cake; cool completely. Run a knife around sides and center tube of pan; remove cake to serving plate.

For frosting, melt semisweet chocolate and butter in a small saucepan over low heat. Stir in cream and vanilla. Remove from the heat; whisk in confectioners' sugar until smooth. Immediately spoon over cake. Makes 16 servings.

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