- Unsalted butter, room temperature, for greasing soufflé cups
- Sugar, for coating greased soufflé cups
- 6 oz semisweet chocolate, chopped into small pieces
- 6 large eggs at room temperature
- 2/3 cup sugar, divided
- 1/2 tsp kosher salt
- 2 Tbsp heavy cream
- 1 tsp vanilla extract
Preheat oven to 350° and place a rack in center. To prepare soufflé molds, grease inside surface of 8 (6 oz) individual soufflé dishes or ramekins with softened butter. Sprinkle inside of each with sugar, tipping to coat evenly. Set on a rimmed baking sheet.
To prepare soufflé base, place chocolate pieces in top of a double boiler. Place over medium heat and stir until chocolate melts.
Separate eggs, placing yolks in bowl of a stand mixer fitted with a paddle attachment and whites in a large mixing bowl. Add 1/2 cup of sugar and salt to egg yolks. Beat on medium-high speed until very light, fluffy, and thick, 3-4 minutes. Mixture should be thick enough that when paddle attachment is lifted, an egg yolk “ribbon” falls that takes 3-4 seconds to dissolve. Set aside.
Stir cream and vanilla into melted chocolate, and transfer to a large bowl. Stir 1/3 of egg yolk mixture into chocolate mixture. Fold remaining egg yolk mixture into chocolate mixture in 2 additions. Set aside.
Using a stand mixer fitted with a whisk attachment, beat egg whites on medium speed until fluffy but not stiff, 3-4 minutes. Sprinkle in remaining 1 tablespoon sugar. Beat 1 minute longer on medium speed until whites are shiny and firm but not stiff. Beaten whites should form a soft peak when whisk is lifted. Stir 1/3 of egg whites into chocolate mixture. Gently fold in remaining egg whites in 2 additions. Divide evenly among prepared soufflé molds, not letting batter drip down sides of ramekins.
Place filled molds, not touching, on rimmed baking sheet and transfer to oven. Bake until soufflés are puffed and cracked on top, 15-17 minutes. Test doneness by gently shaking the baking sheet, as soufflés should jiggle only slightly. If centers are too soft, quickly close oven and bake an additional 2-3 minutes. Serve immediately.