1 Boil the pasta: Heat 4 quarts of water with 2 Tbsp salt in a large pot on high heat (for pasta). When the water comes to a boil, add the pasta and cook uncovered at a rolling boil for 2 minutes less than the time given on the pasta package instructions. (You want to cook the pasta al dente because it will continue to cook with the cheese mixture.) Rinse quickly in cold water to stop the cooking, drain and set aside.
2. Steam the broccoli: While the pasta water is coming to a boil, steam the broccoli. Put a steamer rack in a pot with an inch of water. Bring to a boil. Add the broccoli florets, sprinkle with a little salt, and cover. Steam for 4 minutes. Then remove the broccoli from the pot to a bowl.
3. Heat the milk: In a microwave or in a small pot on the stovetop, heat the milk until steamy. (Preheating the milk saves time in the next step when you are making the bechamel sauce.)
4. Preheat oven broiler at 500°F.
5. Make roux with butter and flour: Melt 4 Tbsp butter in a thick-bottomed oven-safe pot on medium high heat. When the butter is melted and starts to foam sprinkle with 3 Tbsp of flour. Whisk to combine. Lower the heat to medium and cook for 1 to 2 minutes.
6. Add milk and spices to roux: Pour in the hot milk and whisk vigorously to combine, breaking up any clumps of flour. Lower the heat to medium low and let cook, whisking frequently, until the sauce is smooth and thick enough to coat the back of a spoon. Stir in the dry mustard, paprika, nutmeg, black pepper, Worcestershire sauce, and 1 teaspoon of salt.
7. Whisk in cheeses: Whisk in 1 1/2 cups grated cheddar and the 1/2 cup of Parmesan cheese. Stir until the cheese is melted and the sauce is smooth.
8. Stir in broccoli, top with cheese, broil: Stir in the broccoli and the pasta until well combined. Sprinkle the remaining 1/2 cup grated cheddar cheese on top and place under preheated broiler for 5 to 7 minutes until bubbly and lightly browned.
Thank you to Elise Bauer for this delicious recipe!