- Portion size 12 servings
Preheat oven to 350°F (180°C).
In bowl, sift flour with 3/4 cup of the sugar; sift again into separate bowl. Set aside.
In large bowl, beat egg whites until foamy. Add lemon juice, cream of tartar and salt ; beat until soft peaks form. Beat in remaining sugar, 2 tablespoons at a time, beating until stiff glossy peaks form. Sift flour mixture over top, one-quarter at a time, gently folding in each addition until blended.
Stir espresso powder with vanilla; fold into batter. Gently fold in chocolate until evenly distributed.
Scrape into ungreased 10-inch (4 L) tube pan. Run spatula through batter to eliminate any large air pockets; smooth top. Bake in centre of oven for 40 to 45 minutes or until cake springs back when lightly touched.
Turn pan upside down and let hang on legs attached to pan or on inverted funnel or bottle until completely cool.
Run thin paring knife around edge of cake to unmould from pan. (Cake can be stored in airtight container for up to 1 day or wrapped in plastic wrap or foil and frozen in rigid airtight container for up to 1 month.)