Make a bisque : Fry the crayfish and flambé with cognac. Add the tomato concentrate, leek and carrot. Add white wine, then water to cover and simmer for 2 hours.
Make a roux : Melt 5oz of butter then add flour and the bisque stock to make a thick sauce. Pass the bisque through a conical sieve then add the roux.
Celery root risotto:
Finely dice the celery root and blanch it in boiling water for 3 minutes.
Add the chicken stock, add the Mascarpone and the grated Comté. Season with salt and pepper.
Put the head of celery in the centrifuge and collect the juice. Blend the green curry paste with the warm celery juice and 2oz of butter with a stick blender.
French quenelle bun:
Poach the quenelles in a saucepan of boiling water for 10 minutes, then put them in a terracotta dish before covering them with the Nantua sauce.
Bake in the oven at 230°C / 445°F for 15 minutes.
Plating:
In a soup plate, put the risotto in the bottom, put 1 quenelle on top and coat with the Nantua sauce. Add the celery emulsion and serve.