Step 1: Melt the Chocolate
Finely chop the dark chocolate and place it in a heat-safe bowl. Create a double boiler by setting the bowl over a saucepan with about 1 inch of simmering water (make sure the bottom of the bowl doesn’t touch the water). Stir occasionally until the chocolate is completely melted and smooth, about 3-5 minutes. Remove from heat and let cool for 5 minutes until just warm to the touch, not hot. If the chocolate is too hot, it will deflate your whipped cream later.

Step 2: Prepare the Egg Mixture
In a separate heat-safe bowl, whisk together the egg yolks and 2 tablespoons of the sugar until well combined and slightly pale. Place the bowl over the same simmering water (wipe the pan first if needed). Whisk constantly for 2-3 minutes until the mixture thickens slightly and reaches 160°F on a thermometer (this pasteurizes the eggs for safety). Remove from heat immediately and whisk in the vanilla extract and salt. Let cool for 5 minutes.

Step 3: Combine Chocolate and Eggs
Gradually add the warm egg mixture to the melted chocolate in three additions, whisking constantly after each addition until smooth and glossy. If you add it all at once, the chocolate might seize. The mixture should be smooth and pourable. Set aside to cool to room temperature, stirring occasionally (this takes about 10-15 minutes).

Step 4: Whip the Cream
In a large, cold mixing bowl, combine 1½ cups of the cold heavy cream with the remaining 2 tablespoons of sugar. Using an electric mixer, beat on medium-high speed until soft peaks form (when you lift the beaters, the peaks fold over on themselves), about 2-3 minutes. Be careful not to overwhip, or you’ll end up with butter!

Step 5: Fold Cream into Chocolate
Using a rubber spatula, add about one-third of the whipped cream to the cooled chocolate mixture. Gently fold it in using a circular motion, cutting through the center and folding over. This lightens the chocolate mixture. Then gently fold in the remaining whipped cream in two additions, being careful not to deflate the mixture. Fold just until no white streaks remain. The mousse should be light, airy, and uniform in color.

Step 6: Portion into Serving Dishes
Divide the chocolate mousse among 6 serving glasses, ramekins, or dessert cups. You can spoon it in for a rustic look, or transfer to a piping bag and pipe for elegant swirls. Smooth the tops with an offset spatula if desired.

Step 7: Chill
Cover each serving glass with plastic wrap (press it directly on the surface to prevent a skin from forming, or leave a small gap if you don’t mind a slight skin). Refrigerate for at least 3 hours, or up to 3 days. The mousse needs this time to set properly and develop its full flavor.

Step 8: Garnish and Serve
Just before serving, top with a dollop of freshly whipped cream, chocolate shavings, a dusting of cocoa powder, fresh berries, or a sprig of mint. Serve chilled and watch everyone’s eyes light up!