Light and airy, yet rich with chocolate, this classic soufflé is sheer decadence—and with Chef Boulud’s instruction, mastering this gravity-defying dessert is within your reach. Just follow his tips for preparing the ramekins and whipping the egg whites, and you’ll be amazed by how something so deliciously impressive can be so easy to make.
Prepare ramekins: Brush ramekin with butter to evenly coat the entire interior, from the bottom of the ramekin to the top of the rim. Add a few tablespoons of sugar to the ramekin, then spin the ramekin around to coat the bottom and the walls, pouring the excess into a mixing bowl. (The sugar coating provides a rough surface for the soufflé to adhere to as it bakes, allowing for a taller rise.) Repeat with other ramekins. Chill until ready to use.
Preheat the oven to 375 F. Prepare a double boiler: Add enough water to a 1-quart saucepan to fill halfway, and bring to a simmer. Fit a heatproof glass bowl snugly on top of the saucepan, making sure the bottom of the bowl isn't touching the surface of the water. Add chocolate to the bowl and allow it to melt, stirring occasionally. Meanwhile, in a small bowl whisk together the milk and cornstarch. Pour mixture into a small saucepan over low heat and whisk; once the mixture is simmering, continue to whisk until thickened, about 1 minute. When the chocolate has melted, remove the bowl from the saucepan. Slowly add the milk-cornstarch mixture into the melted chocolate, whisking constantly, until it's thoroughly combined. Add egg yolks and whisk until thoroughly combined and shiny. Set aside.
In a stand mixer fitted with the whisk attachment, add egg whites and a pinch of salt. Starting on low then coming up to medium speed, whip until soft peaks form; then continue whipping as you slowly add the sugar in a steady stream. Once medium peaks form, 1–2 minutes later, turn the motor off and remove whisk. Finish whisking by hand to form medium-stiff peaks. (This prevents the machine from over-whipping, which can cause the soufflé to fall.)
Use a rubber spatula to stir ⅓ of the whipped whites into the chocolate mixture. Then very gently fold in the rest of the egg whites, being careful not to overmix; the goal is to make sure the egg whites retain their airiness. When the chocolate and egg whites are just mixed, fill each ramekin to the rim. Run the tip of your thumb around the inner rim of the ramekin to wipe off the butter and sugar from the top ¼ inch. This prevents the soufflé from sticking to the rim as it bakes, allowing it to rise straight up.Place ramekins on a rimmed baking sheet lined with parchment paper, then into the oven. Bake until the soufflés have risen about ½–1 inch above the rim, 7–9 minutes.
When soufflés have fully risen, remove from oven. Dust with powdered sugar, if using. Shape quenelles of unsweetened whipped cream (optional): Pass about a tablespoon of whipped cream back and forth between two spoons, smoothing and shaping it until you have formed an egg-shaped dollop, or "quenelle." Make a small opening in the top of the soufflé and nestle the quenelle into the hole. Serve immediately. (Note: Soufflés will fall quickly as they cool, so work quickly once they are out of the oven!)