To rice potatoes: place potatoes in a saucepan with water to cover. Bring to a boil, and cook for 20 minutes, or until tender. Drain potatoes, and cool slightly. Hold the ricer over a bowl and force the potatoes through the sieve until completely processed. You will need 1 cup riced potatoes for the recipe.
Preheat oven to 325 degrees F (165 degrees C).
Sift together flour, baking powder, cloves and cinnamon; set aside.
Beat butter and sugar with an electric mixer until light and fluffy. Add yolks, one at a time, beating well with each addition. Add 1 cup riced/mashed potatoes, heavy cream, ground almonds, grated chocolate, and lemon zest and mix well.
Blend in flour mixture and mix until combined. Beat egg whites with an electric mixer until medium-stiff peaks form.
Fold 1/3 of the egg whites into batter to lighten it, then fold in remaining egg whites until no streaks remain.
Pour batter into a 9-inch springform pan. Bake in preheated oven until a toothpick inserted into the center of cake comes out clean, about 1 1/2 hours. Let cool, then frost with chocolate frosting.