Step 1: Melt the Chocolate

• Break the dark chocolate into small pieces and place them in a microwave-safe bowl.
• Add 2 teaspoons butter.
• Microwave in 20-second intervals, stirring after each interval until the chocolate is fully melted and smooth. Set aside to cool slightly.

Step 2: Whip Part of the Cream

• In a cold bowl, whip ½ cup of the heavy whipping cream until it reaches soft peaks. Set it aside in the refrigerator to stay chilled.

Step 3: Separate the Eggs

• Carefully separate the 3 large eggs, placing the yolks into a small heatproof glass bowl and the whites into a large, clean mixing bowl. Set aside.

Step 4: Prepare the Egg Yolk Mixture (Sabayon Method)

• Fill a small saucepan with about 1 cup water and bring to a gentle simmer.
• To the bowl with egg yolks, add 2 tablespoons sugar and 2 tablespoons amaretto liqueur.
• Place the bowl with yolks over the simmering water (make sure the bowl does not touch the water).
• Continuously whisk the egg yolk mixture until it becomes pale, fluffy, thickened, and reaches about 160°F (71°C) on an instant-read thermometer. Remove from heat immediately.

Step 5: Combine the Chocolate with Egg Yolks

• Gently fold the slightly cooled melted chocolate mixture into the egg yolk mixture. Blend until fully combined and smooth. Set aside.

Step 6: Whip Egg Whites

• Using clean beaters or a whisk attachment, beat egg whites with a pinch of salt until foamy.
• Gradually add the remaining 1½ teaspoons sugar, and continue whipping until stiff, glossy peaks form.

Step 7: Fold Egg Whites into Chocolate Mixture

• Add about ½ cup of whipped egg whites into the chocolate mixture to lighten it.
• Gently fold the chocolate mixture into the remaining egg whites, being careful to keep as much air in the mixture as possible, until thoroughly combined.

Step 8: Incorporate Whipped Cream

• Carefully fold the chilled whipped cream from Step 2 into the chocolate-egg mixture.
• Use gentle, sweeping motions, being cautious not to deflate the mousse.

Step 9: Chill the Mousse

• Divide the mousse evenly among individual ramekins or serving glasses.
• Cover each serving with plastic wrap.
• Refrigerate mousse for at least 4 hours, preferably overnight, until fully set.

Step 10: Prepare Amaretto Whipped Cream (optional garnish)

• Just before serving, whip the remaining ¼ cup of heavy whipping cream along with 2 teaspoons amaretto and 1 teaspoon sugar until soft peaks form.

Step 11: Serve with Optional Toppings

• Remove the mousse from the refrigerator just before serving.
• Garnish each mousse with a dollop of amaretto whipped cream, toasted almonds, and chocolate shavings or curls, if desired.