1 pound good quality bittersweet chocolate, chopped into pieces 8 ounces fresh unsalted butter, cut into pieces 10 large eggs, separated 1/4 cup organic sugar 1/4 cup flour Butter 10-inch springform pan or non-stick cake pan and preheat oven to 400 degrees Over a double boiler, with water simmering at medium-low heat, melt chocolate, stirring occasionally When chocolate has melted completely, stir butter into chocolate until fully combined In another large bowl, beat the egg whites just until they form firm peaks; do not overbeat In a small mixing bowl, whisk the egg yolks and sugar until frothy and lemon-colored; add flour and mix thoroughly Fold the egg yolk mixture into the chocolate mixture Add one-third of the egg whites to the chocolate mixture, mixing thoroughly Add remaining egg whites, very gently and slowly folding until no white streaks remain Pour into prepared pan and bake for just 15 minutes Remove from oven and cover with plate or tight-fitting lid; let steam with lid for 12 minutes more Serve at room temperature