- Pulse biscuits in a food processor until they become fine crumbs. Place crumbs in a large bowl and stir in melted butter.
- Pack firmly into the bottom of a tart 9-inch pan and refrigerate for 15 minutes.
- Place egg yolks, crème de menthe, and sugar in a large mixing bowl over a pan of boiling water and whisk for 2 minutes. Remove the bowl from the heat and whisk until the mixture is cold.
- Soften the gelatin in 1 tablespoon water in a small pan and place over low heat to warm and dissolve the gelatin. Whisk gelatin into the egg mixture.
- Whip egg whites until stiff and fold into the egg mixture, then spoon onto the biscuit base. Refrigerate for 2 hours.
- Whip the heavy cream in a large bowl until stiff and spread it on top of the set egg mix. Decorate with chopped mint Aero bar or grated chocolate.