Melt Chocolate: Melt the dark chocolate in a heatproof bowl set over a pan of simmering water. Once melted, remove from heat and let cool slightly.
Whip Egg Yolks: In a separate bowl, whip the egg yolks with one tablespoon of sugar until thick and pale.
Combine Chocolate and Yolks: Gently fold the melted chocolate into the egg yolk mixture.
Whip Egg Whites: In another bowl, whip the egg whites until soft peaks form. Gradually add the remaining tablespoon of sugar, continuing to whip until stiff peaks form.
Fold Egg Whites into Chocolate: Gently fold the egg whites into the chocolate mixture in two additions.
Whip Cream: In a separate bowl, whip the heavy cream until it forms soft peaks. Fold this into the chocolate mixture until no white streaks remain.
Set Mousse: Divide the chocolate mousse among serving glasses or bowls, filling them halfway. Chill in the refrigerator while you make the matcha mousse.
Matcha Mousse:
Sift Matcha: Sift the matcha powder to remove any lumps.
Whip Cream and Sugar: Whip the heavy cream with sugar and vanilla extract until it forms soft peaks.
Add Matcha: Gently fold the sifted matcha into the whipped cream until fully incorporated.
Layer Mousse: Spoon or pipe the matcha mousse over the chilled chocolate mousse in each glass.
Chill: Refrigerate the mousses for at least 2 hours, or until set.
Serve: Garnish with a dusting of matcha powder or chocolate shavings before serving.