For the vanilla casserole on plum sorbet on Armagnac sauce, prepare a roux and gradually add the milk (Prepare a choux pastry). Add vanilla pulp.
Gently fold in 4 egg yolks, beat egg whites with sugar until stiff, fold into choux pastry mixture. Pour into a ramekin greased with butter and sprinkled with sugar. Cook in a bain-marie (160 °C) for 45 minutes.
For the plum sorbet, boil the sugar and water for 3 minutes, then blend with 500 g of pitted plums, season with the juice of one lemon and cinnamon, then fold in the softened gelatine. Freeze in the ice cream maker until creamy.
For the Armagnac sauce, boil the whipping cream, stir the egg yolks and sugar, mix with the whipping cream, heat over low heat until the sauce thickens. Season with Armagnac. Serve the vanilla casserole with plum sorbet on Armagnac sauce sprinkled with powdered sugar and garnished with a mint leaf.