2 tbspunsalted butter, room temperature, plus more for ramekins
granulated sugar, plus 1/3 cup for batter, plus more for ramekins
3large egg whites, room temperature
3large egg yolks
0.125 tspcream of tartar
5.5 ozbittersweet chocolate (70% cacao), melted
0.667 cupwhole milk
1 tbspcornstarch (plus 1½ teaspoons)
0.125 tspsalt
3 tbspcrème fraîche or sour cream
confectioners' sugar, for dusting
Method
1Preheat oven to 400°F. Brush four 7-ounce ramekins generously with the butter; coat with granulated sugar. Whisk egg whites until frothy, about 2 minutes. Add cream of tartar; whisk until soft peaks form. Add 1/3 cup granulated sugar; whisk until medium peaks form, about 5 minutes.
2Set chocolate in a bowl. Whisk milk into cornstarch and salt in a saucepan. Bring to a simmer. Cook, stirring, until thick, 1 to 2 minutes. Whisk into chocolate (mixture will separate). Whisk in yolks and crème fraîche. Gently fold in egg whites.
3Fill ramekins evenly with batter. Bake on a baking sheet, rotating halfway through, until soufflés rise but centers are still liquid, about 14 minutes. Dust with confectioners' sugar and serve immediately.