Cut the sea scallops in thin slices and arrange them on a small piece of foil in a rosette pattern.
Steam the celery root briefly and let it cool before you mix the mayonnaise and the mustard to it. Mix the olive oil and the lemon juice together, add the cayenne pepper. Lightly brush the scallops with the vinaigrette and put them under the broiler until cooked.
On a plate place the mache leaves around like the petals of a flower. Place the celery root salad in the middle and slide the scallops off the foil on top of the celery. Sprinkle a little more spicy dressing on top and serve