1) Preheat the oven to 350°F and place the oven rack in its lowest position.
2) Whisk together and then sift the gluten-free multi-purpose blend, cocoa, cornstarch, 3/4 cup sugar, espresso powder or almond flavoring, and baking powder. Set aside.
3) In a large clean, grease free mixing bowl, beat the egg whites until foamy. Beat in the salt and cream of tartar.
4) Gradually increase the speed of the mixer, and beat until the egg whites have increased in volume and thickened significantly.
5) Gradually beat in the 3/4 cup + 2 tablespoons sugar, a bit at a time, until the meringue holds soft peaks.
5) Gently fold in the sifted flour/sugar blend, ¼ cup at a time, just until mostly blended. The cocoa makes it hard to blend in completely evenly, so leaving a slightly marbled effect is perfect.
6) Spoon the batter into an ungreased, 10? round angel food pan.
7) Bake the cake until the top springs back when pressed lightly, about 45 minutes.
8) Remove the cake from the oven and invert the pan onto the neck of a heatproof bottle or funnel, to suspend the cake upside down as it sets and cools, about 2 hours.
9) Remove the cake from the pan by running a thin spatula or knife around the edges of the pan, turning it over, and gently shaking the cake loose onto a serving plate.
10) Serve with whipped cream and chocolate sauce, if desired. Wrap any leftovers airtight, and store at room temperature.
Yield: one 10" cake, about 12 to 16 servings.
*Make your own blend
Many of our gluten-free recipes use our King Arthur Gluten-Free Multi-Purpose Flour, which includes ingredients that reduce the grittiness sometimes found in gluten-free baked goods. Our flour also increases the shelf life of your treats, keeping them fresh longer.
The following make-at-home blend, featuring stabilized brown rice flour, works pretty well when substituted; and it tastes better than a blend using regular brown rice flour.
Whisk together 6 cups (28 1/2 ounces) King Arthur stabilized brown rice flour; 2 cups (10 3/4 ounces) potato starch; and 1 cup (4 ounces) tapioca flour or tapioca starch. Store airtight at room temperature. Note: You can substitute white rice flour for the brown rice flour if you like; it'll make your baked goods grittier (unless you manage to find a finely ground version).