Peel egg and coarsely chop. Into a blender, add egg, arugula, chervil, parsley, 3 tablespoons water, the lemon juice and the 1/3 cup olive oil. Process to a fine purée. Season to taste with salt and pepper. Set aside.
03Put fish in the oven and bake 12 to 15 minutes, until just cooked through. Spread sauce on each of 4 warm dinner plates. Cut each fillet in four pieces and place two pieces on each plate, on the arugula sauce. Season fish with salt and pepper. Garnish with arugula and serve.