French onion green bean casserole

Slice the onions with the grain rather than across it, so the pieces hold together.

Heat butter in a large skillet over medium heat, add the onions and a pinch of salt, and cook until caramelized, soft and browned, about 15 minutes.

For the white sauce, melt butter in a saucepan over medium heat, whisk in flour and cook it about three minutes.

Whisk in cold milk slowly at first, then faster; season with salt, cayenne, freshly grated nutmeg and a pinch of dry thyme.

Bring to a simmer on medium heat, stirring with a spatula, and cook two or three minutes until thickened. Turn off and set aside.

Trim the beans by lining them up and slicing both ends off, then cut them in half.

Boil the beans in salted water three or four minutes, just to take the raw edge off, so they stay crisp. Lift out with a strainer and drain very well.

Spread half the caramelized onions in the bottom of a 9x13 casserole dish.

Add the drained beans, spread out with tongs, and season with salt and pepper.

Spread the white sauce over evenly, then half the gruyere, then the rest of the onions pressed down with the back of a spoon.

Mix the breadcrumbs with a little melted butter and sprinkle evenly over the top, then the last half of the gruyere and a dusting of parmesan.

Bake at 375F for about 30 minutes, then rest 10 to 15 minutes to solidify before serving.