Preparation Steps

• For the chocolate mousse: In a medium bowl, whisk together 0.5 cup heavy cream, 0.25 cup granulated sugar, and 0.3 ounce cocoa powder until well combined.
• In a small saucepan, whisk together 0.5 cup milk and 1 egg yolk. Cook over medium-low heat, stirring constantly, until the mixture thickens slightly and coats the back of a spoon (about 5-7 minutes). Do not boil.
• Remove the milk mixture from heat and immediately pour it over the chopped bittersweet chocolate in a heatproof bowl. Let stand for 5 minutes, then whisk until smooth and melted.
• Gently fold the melted chocolate mixture into the cream mixture until just combined.
• For the whipped cream: In a separate bowl, beat 1 cup heavy cream, 2 tablespoons powdered sugar, and 0.5 teaspoon vanilla extract until stiff peaks form.
• To assemble the parfaits: Spoon a layer of chocolate mousse into the bottom of each serving glass. Top with a layer of whipped cream. Repeat layers until the glasses are full.
• Chill for at least 30 minutes before serving. Garnish with chocolate shavings and fresh berries if desired.