Position a rack in the center of the oven. Preheat the oven to 400°F. Butter a 9-by-13-inch baking dish. Bring a large pot of salted water to a boil.

Lightly smash and peel the garlic. Thinly slice the cloves.

Grate the cheeses on the large holes of a box grater.

Strip the leaves of the leafy greens from the stems. Tear them into bite-size pieces.

When the water boils, stir in the pasta and cook just short of al dente, 2 minutes shy of the package directions. Drain the pasta. Reserve the pot.

Open the beer. In the same pot you cooked the pasta in, melt 4 tablespoons unsalted butter over medium-high heat. Add the garlic and cook, stirring constantly, until soft and fragrant, 1 minute. Sprinkle the flour over the garlic and cook, whisking, for 1 minute. Gradually whisk in the beer until smooth.

Whisking continuously, slowly add the heavy cream. Once incorporated, gradually add the whole milk. Bring to a simmer and cook, whisking, until slightly thickened, 2 minutes. Reduce the heat to low and add the grated cheeses and the Parm. Stir until nearly completely melted. Stir in the Dijon mustard and Worcestershire sauce. (The recipe calls for 3 tablespoons of each, but taste and add as you see fit.)

Season the sauce with 1½ teaspoons of salt and lots of freshly ground black pepper. Stir the pasta into the cheese sauce, followed by the torn greens, stirring to distribute them evenly. They’ll cook down further in the oven.

Transfer the contents of the pot to the prepared baking dish. Bake until the top is golden and beginning to crisp, 15 to 20 minutes.

Meanwhile, in a medium skillet, melt the remaining 2 tablespoons of unsalted butter over medium-high heat. Add the panko breadcrumbs and toast, stirring often, until deeply golden brown, 4 to 6 minutes. Transfer the breadcrumbs to a bowl and season with salt.

Remove the baking dish from the oven, scatter the breadcrumbs evenly over the pasta and return the dish to the oven. Continue to bake until the top is deeply golden brown and the sauce is thick and bubbling, 12 to 16 minutes. Let cool for 15 minutes before serving.