Bring a large saucepan of water to a rolling boil with the lemon, cloves, and peppercorns. Add the rutabagas (it helps to do this in a large sieve or a chinoise), boil for about two minutes, remove and drain. Repeat with the carrots, parsnips, and mirlitons. (The mirlitons will only require about one minute.)
Crush the garlic cloves, and use them to wipe the inside of a two-inch-deep, 12-by-9-inch glass baking dish. Discard what's left of the garlic.
Layer the vegetables in the baking dish, in the order listed. Sprinkle a mixture of the cheeses between the layers. Season with white pepper and (sparingly) nutmeg. The cheeses will provide all the salt this needs.
Combine the whipping cream and the egg yolks thoroughly. Pour the mixture over the vegetables. Cover with aluminum foil, and bake in the preheated 400-degree oven for one hour.
Remove the foil, sprinkle bread crumbs in a thin layer over the top, and return to the oven. Continue baking until the crust browns.
Remove from the oven and allow to rest and cool for at least ten minutes before serving. This is better warm than hot.