Halve the fennel bulbs and cut into strips. Juice orange (1), boil juice with water and salt, steam fennel strips in it for 10 min until soft.
Peel orange (2) thickly and cut into slices. Layer with fennel and olives in a greased baking dish. Boil orange stock a little. Mix in the hollandaise sauce, season and pour over the vegetables. Sprinkle with nuts.
Briefly gratinate under the broiler or in the oven on the highest setting.