Zucchini Gratin

6 Tbs butter
3 large yellow onions, sliced
4 medium zucchini, sliced 1/4 inch thick
2 tsp salt
1 tsp pepper
1/4 tsp nutmeg
2 Tbs flour
1 c hot milk
3/4 c bread crumbs
3/4 c grated gruyere or cheddar cheese

Preheat the oven to 400 degrees.
Melt the butter in a very large (12inch) saute pan and cook the onions over low heat for 20 minutes, or until tender but not browned. Add the zucchini and cook, covered, for 10 minutes, or until tender. Add the salt, pepper, and nutmeg and cook uncovered for 5 more minutes. Stir in the flour. Add the hot milk and cook over low heat for a few minutes, until it makes a sauce. Pour the mixture into an 8x10 inch baking dish.
Combine the bread crumbs and cheese and sprinkle on top of the zucchini mixture. dot with 1 tbs of butter cut into small bits and bake for 20 minutes, or until bubbly and browned.

Makes a very large pan, but this recipe can be halved easily.