1. Prepare the Egg Yolk Mixture:

In a medium bowl, whisk together the egg yolks and ¼ cup of the granulated sugar until the sugar is dissolved and the mixture is lightened in color, about 1 minute. This creates a smooth, pale yellow mixture.

2. Heat the Cream: In a small pot, combine 1 cup of the heavy cream and the salt.

Bring just to a simmer over medium heat. Watch carefully – you want to see small bubbles forming around the edges of the pot, but do not bring it to a full boil.

Once simmering, remove from the heat.

3. Temper the Egg Yolks: Remove ¼ cup of the warm cream mixture from the pot.

Slowly drizzle it into the egg yolk mixture, whisking constantly. This is called “tempering” the egg yolks, and it prevents them from scrambling when added to the hot cream.

4. Combine and Cook: Transfer the warmed egg yolk mixture to the pot with the remaining heavy cream.

Whisk well to combine.

Return the pot to medium-low heat.

Stir frequently with a rubber spatula, scraping the bottom and corners of the pan, until the mixture thickens just enough to coat the spatula. The temperature should be between 160°F to 180°F (71-82°C) on an instant-read thermometer. Be careful not to overheat.

5. Add Chocolate (and Espresso):

Remove from the heat.

Stir in the chopped chocolate and espresso powder (if using) until the chocolate is completely melted and the mixture is smooth.

6. Cool the Chocolate Mixture: Transfer the chocolate mixture to a large bowl.

Refrigerate for 20 minutes, stirring halfway through, until slightly cooled. Do not refrigerate for too long, or the chocolate will harden and make it difficult to fold in the whipped cream.

7. Whip the Cream: In another large mixing bowl, combine the remaining 1 ½ cups of heavy cream, the remaining 2 tablespoons of sugar, and the vanilla extract (if using).

Using an electric handheld mixer (or a stand mixer), whip the cream until it is fluffy and forms soft peaks. This means the whipped cream should hold its shape softly but not be stiff.

Reserve ½ cup of the whipped cream in the refrigerator for serving.

8. Fold in the Whipped Cream: Stir a large dollop (about ⅓) of the whipped cream into the cooled chocolate mixture until thoroughly combined. This lightens the chocolate mixture.

Add the remaining whipped cream.

Using a rubber spatula, gently fold the whipped cream into the chocolate mixture. Scoop the chocolate mixture from the bottom of the bowl and fold it over top of the cream. Repeat this folding action, moving around all sides of the bowl, until the cream and chocolate are thoroughly combined. Be gentle.

9. Divide and Chill (Optional):

Divide the mousse mixture among 6 (6-ounce) ramekins or dessert glasses.

Serve immediately, or refrigerate for up to 1 hour to chill slightly.

10. Serve: Serve with the reserved whipped cream, chocolate shavings, and raspberries on top, if desired. Enjoy!