1 large head broccoli, cut into 1 to 2 inch florets, tender stems peeled and cut in ½ inch slices (about 5 cups)
Kosher salt 4 tablespoons unsalted butter, plus 1 tablespoon melted, plus more for the casserole
1 tablespoon chopped fresh sage
5 tablespoons all purpose flour
3 tablespoons dry sherry
1 cup low sodium chicken stock
1 cup milk
1 cup heavy cream
Pinch freshly grated nutmeg
Freshly ground black pepper
Squeeze of fresh lemon juice, to taste
1 cooked chicken (or left over turkey meat) meat removed and cut in chunks, skin and bones discarded (about 3 to 3 1/2 cups meat)
1 bunch scallions, chopped (about 1 cup)
1 ½ cups grated gruyere
½ cup sliced or slivered almonds, toasted
½ cup grated parmesan
1/4 cup breadcrumbs
Preheat the oven to 400 degrees. Butter a 3 quart shallow casserole dish and bring a large saucepan of salted water to boil. Boil the broccoli until bright green and almost tender (you still want it to have a little bite, it will cook more in the oven). Cool under cold running water and pat very dry.
In a large saucepan, melt the 4 tablespoons butter over medium heat. When the butter is melted, add the sage and let sizzle a minute, then add the flour. Cook and whisk the roux or else it will taste like raw flour, about 3 minutes, without letting it brown. Pour in the sherry and cook to reduce it away, about 1 minute. Whisk in the stock, milk, cream and nutmeg and season with salt and pepper. Bring to a simmer and cook, whisking occasionally to get out any lumps, until thickened, about 6 to 7 minutes. Stir in the scallions and gruyere until the cheese is melted, then remove from heat.
In a large bowl, mix the almonds, chicken and broccoli with the sauce until thoroughly coated. Pour into the prepared casserole dish. In a small bowl, toss together the parmesan, breadcrumbs and melted butter. Sprinkle the mixture over the top of the casserole. Bake until browned and bubbling, about 35 minutes.