First of all, let’s prepare moistener - put 40 g sugar, 80 g water and 5 g mint in a saucepan and boil for 2-3 minutes. Cool with mint, then strain off. Place aside the moistener before use.
To prepare the cream, boil 300 g milk and 5 g mint. Remove from fire and simmer for 1 hour, then strain. You will no longer need mint. Put the saucepan with milk back on the fire. Whisk 3 egg yolks and 60 g sugar in a large bowl. When the mass is combined and lightened, add 30 g corn starch, mix well. Pour a portion of boiled milk over the eggs in a bowl, stir until smooth, pour in the remaining milk, stir again and return in the saucepan. Boil the cream on a medium heat by stirring continuously, with a hand mixer. Boil for 3 minutes. Remove from fire and add 30 g butter (kept at room temperature) in the saucepan and stir well until the butter melts. Replace the cream into a clean bowl and cover with plastic wrap. Wait until the cream is cold.