Quarter half the cherries and in a small bowl, mix with 2 tbsp sugar. Set aside.
In a large saucepot. heat 3/4 cup of cream until just hot.
Whisk egg yolks, remaining sugar, and a pinch of salt in a medium bowl. Slowly add the hot cream to the egg mixture, whisking continuously.
Transfer the mixture back into the pot, add the chocolate, and cook over low heat, stirring constantly until smooth, about 5-7 minutes. Do not boil. Remove from heat and stir in vanilla.
In a large mixing bowl, whip 1-1/4 cups of cream until stiff peaks form. Gently mix in about a fourth of the cream to the chocolate mixture. Fold in the remaining whipped cream, keeping it airy. Cover and chill for at least 2 hours.
Whip remaining 2 cups of cream until stiff peaks form. Set aside.
Remove mousse from the fridge and spoon a layer into a serving dish. Add a layer of cookie crumbs, then more mouse. Add a teaspoon of chopped cherries, a dollop of whipped cream, and a couple of whole cherries. Serve.
