5 Tbsp butter
3 Tbsp shallots
1 lb brown trumpet mushrooms
2 oz madeira or cream sherry
3 oz crème fraiche or cream
1 bunch leeks
1/4 cup water
2 lbs rutabagas
1 lb celery root
1/4 cup cream
1 Tbsp freshly grated Parmesan
2 Tbsp bread crumbs
Fresh ground pepper to taste
Salt to taste
Chop mushrooms coarsely, keeping in mind that they will shrink to less than half their size. Sauté them gently in 2 Tbsp butter for about 5 minutes, until nearly dry. Chop shallots finely and add to mushrooms with madeira. Reduce madeira until nearly dry and add cream. Reduce cream by 3/4 and season with salt and pepper. Set mushroom mixture aside.
Cut off the dark green part of the leeks and reserve for other purposes. Split remaining leeks in half and soak in tepid water for 5 minutes. Clean inner layers and cut off root. Chop leek finely and add to 1 quart saucepan with 1 Tbsp butter, a pinch of salt, and a little pepper. Cover tightly and cook on low, stirring occasionally, until tender (about 5 minutes). Set aside.
Peel rutabagas and slice thin. Peel celery root and grate coarsely.
Melt 2 Tbsp butter in saucepan and reserve.
Butter the inside of a 6-inch cheesecake pan and arrange an overlapping circle of rutabaga around outer edge. Continue in a concentric circle until bottom is entirely covered. Brush with melted butter. Sprinkle lightly with bread crumbs, then add a thin layer of leeks, then a thin layer of celery root, topped with a 1/4 inch layer of chopped mushroom. Smooth mixture with spatula. Begin second layer of rutabaga and other ingredients and repeat until pan is full. Finish with a layer of rutabaga.
Pour 1/4 cup cream over top and cover tightly with aluminum foil. Bake 400 degrees for 1 hour 15 minutes.
Uncover and test for doneness with long-tined fork. Sprinkle top lightly with bread crumbs, Parmesan, salt and pepper. Dot lightly with butter. Broil in oven until top is golden brown.