Peel squash, seed and cut in half. Slice squash and cut in 1/4 inch slices. A mandoline is useful for this, if you have one. Parboil squash slices for 5 minutes and drain.
Cut onions in half from top to bottom, peel, and slice into half-moons. Caramelize onion in 3 tbsp butter in a heavy saute pan until golden brown.
Melt butter in heavy saucepan and add flour. Cook, stirring constantly, until flour is golden and starts to smell nutty. Add milk, whisking to dissolve all lumps. Add nutmeg and white pepper. Cook until it coats the back of a spoon, and then add cheese, stirring to melt.
Assemble gratin: Put a little sauce in the bottom of a baking dish, add a layer of squash slices, cover with a layer of onion, and pour cheese sauce over. Repeat layers until all ingredients are used or pan is full.
Toss parmigiano and bread crumbs together until well mixed, and sprinkle over gratin. (Note: recipe may be made to this point and then held for up to 24 hours, refrigerated, before baking. Bring back to room temperature before baking.)
I'm a business professional who learned to cook early on, and have expanded my tastes and my skills as I've traveled and been exposed to new cuisines and new dishes. I love fresh vegetables, any kind of protein on the grill, and breakfasts that involve fried eggs with runny yolks. My recipes tend toward the simple and the Southern, with bits of Asia or the Mediterranean or Mexico thrown in here and there. And a peanut butter and jelly sandwich on a float in the lake, as pictured, is a pretty fine lunch!