Split the marrons lengthwise and rinse the stomach cavity clean. Drain and set aside.

Blanch the samphire or asparagus in boiling water until just cooked. Drain, refresh in iced water, drain again and set aside.

Put the fish stock, wine, shallots and lemon aspen fruit or lime juice into a saucepan. Bring to a boil, reduce the heat and simmer until syrupy. Add the orange juice and reduce to approximately 3 tablespoons. Cut 14 tablespoons of the butter into small cubes and gently swirl into the sauce, a few pieces at a time, until all has been incorporated. Taste and adjust seasoning. Strain and keep warm but do not reboil.

Season the marron with salt and pepper. Melt the remaining 2 tablespoons of butter and brush on the marron flesh. Cook over hot charcoal or under a broiler until just cooked through. Quickly reheat the blanched samphire or asparagus with a little butter. Arrange the grilled marron on 4 plates, garnished with the samphire or asparagus and surrounded with the sauce.