8ouncesbittersweet, dark or semi-sweet chocolate, chopped(not unsweetened)
10tablespoonsunsalted butter, cut into pieces(1¼ sticks)
3½tablespoonsall purpose flour
Powdered sugar, for dusting
Preheat oven to 325ºF. Line bottom of 9-inch round cake pan with 2-inch sides with parchment paper. Spray with non-stick baking spray with flour, or butter bottom and sides and dust with flour. Set aside.
Place chocolate and butter in double boiler over simmering water, stir until melted and smooth. Set aside to cool slightly.
In large bowl, whisk yolks and sugar until pale yellow. Mix in flour and the slightly cooled chocolate mixture.
In another bowl, beat the egg whites with an electric handheld mixer until soft and stiff peaks form but not too dry. Fold whipped egg whites into chocolate mixture and fold and stir until incorporated with no white streaks.
Pour batter into prepared pan and bake 25 to 35 minutes until toothpick inserted in middle has just a few attached crumbs. Let cake cool completely in pan on a rack.
Run sharp knife around sides of pan and turn cake out onto plate or platter, remove parchment paper, dust with powdered sugar and serve.
Bittersweet, dark or semi-sweet chocolate will work, look for 60% to 70% cacao content.
Solid chocolate bars work best, just cut into pieces. I used Belgian dark chocolate chunks and that works perfectly fine, as well.
Be careful not to get any yolk in the egg whites when separating or they won't whip properly.
Baking time varies by oven, anywhere between 25 to 35 minutes, mine was perfect at 30 minutes. The cake will have a crackled top with a dense center and just a few crumbs attached to the testing toothpick.