Take two large Spanish onions, wash and skin and tie them to prevent breaking. Put them into a saucepan over the fire, cover with boiling water, cook until they can be pierced with a broom straw--from two to three hours, according to size. When done, drain and carefully take out the centers, leaving about a quarter of an inch for the shell. Have ready a stuffing made from a quarter of a pound of mushrooms prepared as before. Put these and the centers of the onions into a chopping bowl and chop very fine. Cook them together until the moisture from the onions has almost evaporated, then add a generous heaping tablespoonful of butter, a tablespoonful of rich cream, and three heaping tablespoonfuls of grated bread crumbs, salt and pepper to taste. Fill the onion shells with this mixture, smooth the tops nicely, sprinkle with bread crumbs, brush with egg and a little butter. Put in the oven and brown about ten minutes, and serve with the following sauce: Rub a generous heaping tablespoonful of butter and a heaping tablespoonful of flour together. Put a small teacup of milk into a saucepan on the fire, when hot stir in the butter and flour and a quarter of a pound of mushrooms prepared as before and chopped very fine, season with salt and pepper to taste. Place the onions on a platter and pour the sauce around them, garnish with parsley and serve. STUFFED CELERIAC WITH SPANISH SAUCE. Put over the fire in a saucepan three-quarters of a cup of rich milk and three ounces of butter, let them come to a boil, then add three ounces of dried and sifted bread crumbs and an even tablespoonful of flour. Let it cook, stirring all the time until it is a smooth paste and detaches itself from the sides of the pan, remove from the fire and set it aside to cool. When cold beat three eggs light, stir in a little at a time, beating well until the mixture is smooth and all the beaten egg used, then add a heaping teaspoonful of sugar, three heaping tablespoonfuls of walnut meats chopped fine, two tablespoonfuls of rich cream, and salt and pepper to taste. Take four large, fine celeriac roots, clean, scrub and scrape them. Cut off a slice from the top of each to make a cover, then with an apple corer remove the inside, taking care not to pierce the root, leave a shell a quarter of an inch thick. Fill each with the dressing, leaving fully half an inch at the top for it to swell. Place the cover on each, tie well the roots to prevent breaking in the cooking, stand them in a saucepan with water to reach not quite to the top of the roots, and put in all the celeriac removed from the roots, boil gently until tender--about an hour--adding boiling water from time to time as it evaporates. When they are tender take them out of the water and put them aside, keeping them hot. Strain the water they were boiled in, form what is left from the stuffing into small cylinders, boil five minutes in the strained stock, take them out and put with the roots to keep warm.