Preheat the oven to 350 degrees F. Select a 10 inch cake pan or springform pan; butter and flour the bottom and sides of the pan. Line the bottom of the pan with a greased 10 inch round circle of parchment paper. Line the round edge of the pan with a greased 4 inch wide strip of parchment paper, creating a "collar" that extends about 2 inches above the edge of the pan.
In a double boiler, combine the chocolate and butter and cook, stirring constantly, until melted. Using a wire whisk, stir in the cocoa. Remove from heat and cool for a bit.
Beat the egg yolks together and stir, a little at a time, into the chocolate mixture (making sure that the chocolate mixture isn't piping hot so that it will cook your eggs!)
In a medium bowl, combine the egg whites and sugar and beat mixture until soft peaks form. Gently fold into the chocolate mixture.
Pour the batter into the cake pan and bake in center of oven for 40-45 minutes. The edges will appear cooked while the center will still be moist.
TOPPING
Combine the cream, honey and lemon zest in a medium bowl. Whip until soft peaks form.
Slice cake and garnish with topping and mint sprigs.
Notes
If you want this recipe to be fully gluten-free, just be sure to use a GF chocolate.