For the syrup
Prepare the syrup by boiling the water, sugar and lemon juice for 6' to 7'. Line half of the toasts in a rectangular mold and pour the hot syrup all over them.
Prepare the cream: Put eggs, sugar, flour and vanilla in a bowl and stir them with a whisk. Pour the mixture into the milk, stir it and put it on fire to boil. Reduce the heat and cook the cream for a while, stirring it constantly until it thickens. Remove the cream from heat and when it cools off slightly, add butter and stir.
Beat the vegetable whipped cream in a mixer, add caster sugar and continue beating for 2-3 more minutes.
Pour half of the milk-based cream in the mold with the toasts. Place another layer of toasts with syrup over it and then add the remaining cream. Cover the surface with whipped cream and sprinkle with roasted nuts. Place the dessert in the refrigerator for several hours before serving.