Roasted Marron with Natural Jus, Spring Vegetables and Herbs

• 4 × 300 g (10½ oz) whole raw marrons (freshwater crayfish)
• 30 g (

Kill the marrons by quickly slicing neatly through the middle of the heads down through to the tails. Pick out and discard the coral from the head and remove the intestinal tract from the tail. Heat a saucepan large enough to hold all the marrons (or two pans if you don’t have one big enough) on moderate heat and add half the butter. Season the marrons and place them in the pan