Preheat and prep. Heat your oven to 375°F (190°C). Grease a 9x13-inch baking dish or similar casserole pan.

Cook the pasta. Bring a large pot of salted water to a boil. Add the pasta and cook until just shy of al dente, 1 to 2 minutes less than the box suggests. Drain and set aside.

Toast the topping. In a small skillet, heat a splash of olive oil over medium. Add breadcrumbs, a pinch of salt, and a little paprika. Stir until lightly golden, 2 to 3 minutes. Remove from heat and mix in a handful of Parmesan. Set aside.

Make the roux. In a large pot, melt 4 tablespoons of butter over medium heat. Whisk in 1/4 cup flour and cook for 1 to 2 minutes until it smells nutty and looks smooth, but not browned.

Build the sauce. Slowly whisk in 3 cups of milk, plus up to 1/2 cup cream if using. Keep whisking until the mixture thickens and gently bubbles, 4 to 6 minutes.

Season the sauce. Stir in 1 teaspoon Dijon, 1/2 teaspoon garlic powder, 1/2 teaspoon onion powder (optional), 1/2 teaspoon paprika, 1 teaspoon salt, and 1/2 teaspoon black pepper. Taste and adjust—ham and cheese are salty, so aim for “pleasantly seasoned,” not salty.

Add the cheese. Turn heat to low. Stir in 2 cups grated cheddar and 1 cup Gruyère or Swiss in batches until melted and smooth.

Combine. Add the drained pasta and diced ham to the pot. Stir gently to coat everything in sauce. If the mixture seems too thick, splash in a little milk.

Transfer to the dish. Pour the mixture into the prepared baking dish and smooth the top. Sprinkle with a little extra cheddar and Parmesan for a melty layer.

Add the crunchy topping. Scatter the toasted breadcrumbs evenly over the surface.

Bake. Bake for 18 to 22 minutes, until the edges are bubbling and the top is golden and crisp.

Rest and serve. Let the casserole rest for 5 to 10 minutes so it sets slightly. Garnish with chopped parsley if you like, then serve warm.