Lightly oil six glass ramekins and place them upside down on a rack. Refrigerate to chill.
Soak the gelatine leaves in cold water until softened.
Wash, hull the strawberries, and reserve 6 whole for decoration. Halve the remaining strawberries.
Prepare the aspic: Gently heat the Floc de Gascogne in a saucepan. Wring out the gelatine, add to the warm Floc, and stir until fully dissolved. Let cool slightly.
Make the coulis: Peel and pit the mango, blend the flesh smooth, and mix with cane syrup.
Fill a large bowl with ice cubes and a little water. Remove ramekins from fridge, fill with still-warm aspic, and set in the ice bath for 5 minutes. Invert to drain excess into a bowl, leaving a thin, even layer coating the bottom and sides.
Arrange halved strawberries in a star pattern at the base of each ramekin, pressing more halves against the walls. Refrigerate 15 minutes. Add remaining strawberries, then pour over aspic to cover completely. Chill at least 4 hours.
Unmold onto chilled dessert plates. Drizzle with mango coulis and garnish with reserved strawberries and lemon balm leaves.
