Preheat the oven to 375˚ F.

In a large, heavy-bottom pot, bring salted water to a boil and add the elbow macaroni. Cook according to the package instructions until just al dente, then drain and set aside.

Make sure you have both a whisk and a wooden spoon nearby, and something to rest them on. You will be switching back and forth between the two utensils as you first make a roux and then build on that to make a béchamel.

In the still-hot macaroni pot, heat the butter over medium-high heat until it foams and subsides. Whisk in the flour, then switch to a wooden spoon and stir steadily over medium-high heat until the mixture begins to turn a nutty golden brown, about 2 minutes. Do not let the mixture scorch.

Whisk in the milk and bring the mixture just to a boil, stirring with the wooden spoon and making sure to scrape each part of the surface of the pan so that hunks of flour or milk do not stick. Reduce to a simmer and continue to cook and stir until the mixture is slightly thicker than heavy cream.

Whisk in the mustard powder, cayenne, and Worcestershire, then add half the Parmigiano-Reggiano (you’ll sprinkle the rest over the top) and the rest of the cheeses and, if using, the ham, and stir until the cheeses have melted completely.

Stir in the cooked macaroni and mix well. Remove from the heat and stir in the salt and optional pepper.

Transfer the mixture to a glass or ceramic casserole, top with the remaining Parmigiano, and bake in the oven for 15 to 20 minutes, until the top is golden brown and the mixture is bubbling slightly.

Serve hot, or refrigerate and gently reheat the whole thing, or in portions as needed.