Directions

1. 1

   Set up a double boiler by placing a heat-proof metal bowl over a saucepan of gently simmering water, ensuring the bowl does not touch the water. Add the finely chopped bittersweet chocolate to the bowl and stir constantly until completely melted and smooth. Remove from heat and allow to cool for 2–3 minutes.

2. 2

   While the chocolate cools, lightly butter four 3-inch diameter ramekins or 7–8 ounce jars and set aside on a clean surface.

3. 3

   In a stand mixer or with a hand mixer, beat the egg whites on high speed until they form soft, foamy peaks. Add the lemon juice and continue beating.

4. 4

   Gradually add the granulated sugar to the egg whites, about 1 tablespoon at a time, waiting a few seconds between additions for the sugar to incorporate. Continue beating until stiff peaks form with a glossy, dense texture that holds its shape.

5. 5

   Stir the egg yolks into the cooled melted chocolate until fully combined.

6. 6

   Gently fold one-third of the whipped egg white mixture into the chocolate mixture using a rubber spatula, folding until just a few white streaks remain.

7. 7

   Transfer the chocolate mixture into the bowl containing the remaining egg white mixture and gently fold together until no white streaks are visible and the mixture is uniform.

8. 8

   Carefully spoon the mousse into the prepared ramekins, dividing equally. Gently tap each ramekin on the countertop several times to release any trapped air bubbles.

9. 9

   Cover the ramekins with plastic wrap or lids and refrigerate for at least 2 hours, or until fully chilled and set, before serving.