Preheat oven to 325°F (160°C). Pour hot coffee over the 2/3 cup (150 mL) cocoa powder. Whisk to blend. Stir in buttermilk. Set aside to cool to room temperature. In another bowl, mix flour with baking powder, salt and baking soda. Set aside.
With hand-mixer, beat the 3/4 cup (175 mL) mashed avocado with sugar and vanilla until smooth. Beat in 1/4 cup egg whites at a time, blending in each addition completely before adding the next. With the mixer on low speed, add the flour mixture in 3 parts, alternating with the coffee mixture in 2 parts, beginning and ending with the dry mixture. Scrape down the bowl as needed.
Scrape batter into two greased and parchment-lined 8-in. (20-cm) round cake pans, smoothing tops of batter. Bake on middle rack of oven 50 to 55 min., rotating halfway through baking time, or until a tester comes out clean when inserted into centres. Let cakes stand in pans 10 min. before turning out onto wire racks to cool completely. (Make-ahead tip: Wrap and refrigerate cakes up to 2 days before slicing and icing.)
To make icing, use hand mixer to beat the mashed avocado until smooth. Beat in icing sugar, cocoa and vanilla until light and fluffy.
Cut each cake horizontally into 2 layers. Place a layer on a serving platter; spread top with a generous 1/3 cup (75 mL) icing. Repeat process twice more. Top with last cake layer and spread remaining icing over sides and top of all layers. Refrigerate at least 1 hr. to set icing before serving.
Skip the butter and cream and still enjoy moist, fudgy cake slathered with creamy icing? The secret is velvety avocados that have less saturated fat than butter and other dairy. An added bonus is cake that relies on fat-free Compliments Balance 100% Pure Liquid Egg Whites for tenderness -- no yolks. The deep dark notes of cocoa and coffee shine through while the avocado stays "hidden" in this decadent re-vamped dessert.