- Unsalted butter, melted, for dish
- ½ cup sugar, plus more for dusting
- 5 oz bittersweet chocolate, chopped
- 2 oz semisweet chocolate, chopped
- 1 1/3 cups milk
- 6 large egg yolks plus 8 large egg whites, room temp
- 6 Tbsp all-purpose flour
- 2 Tbsp brandy
- 1 tsp pure vanilla extract
- Pinch cream of tartar
- Crème Anglaise
Preheat oven to 400 F, with rack in lower third. Do not open oven door until ready to bake. Brush outer lip of a 2-qt soufflé dish with melted butter. Tie a sheet of parchment around dish with kitchen twine so it extends 3 inches above rim. Brush inside of dish and collar with melted butter. Dust with sugar (this adds texture, which helps the soufflé climb); tap out excess. Chill dish in freezer 15 minutes. Stir chocolates in a large heatproof bowl set over a saucepan of simmering water until smooth. Scald the milk (heat it until it’s just about to simmer) in a saucepan over medium heat; remove from heat. Using an electric mixer fitted with the whisk, beat 6 Tbsp sugar and the yolks on high until pale, about 4 minutes. On low, beat in flour. Beat in half the hot milk, ladling it in a little at time (this is called tempering and prevents the yolks from scrambling).
Whisk mixture into pan of hot milk; bring to a boil over medium-high heat, whisking. Reduce heat to low; simmer until thick, about 2 minutes. Pour into chocolate. Stir in brandy, vanilla, and a pinch of salt. (This mixture can be refrigerated, 2 days. Rewarm in a heatproof bowl set over a pan of simmering water.) Egg whites are best whipped when they’re at room temperature (they attain more volume). Using a balloon whisk, beat whites and a pinch of salt in a copper bowl until foamy. (Or beat with an electric mixer in a stainless steel bowl with cream of tartar.) Add 1 Tbsp sugar; beat until whites almost hold stiff peaks. Add remaining Tbsp sugar, and beat until peaks are stiff (meaning they stand straight up when whisk is lifted).
Spoon one-third of egg whites onto base (incorporating in batches prevents them from deflating). Fold them in: Cut through center of mixture with a large rubber spatula, then gently turn spatula over. Rotate bowl a quarter turn; continue folding whites and turning bowl until mostly combined. Fold remaining whites into base, one-third at a time. The mixture is ready when the whites are fully incorporated. Pour mixture into prepared dish. Place on a rimmed baking sheet; this helps you move soufflé in and out of oven. Bake 15 minutes. Reduce temperature to 375 F; bake until set, 20 minutes. Remove collar; serve immediately with crème anglaise if desired.