Prepare the pasta noodles as per the instructions on the packaging.
In a large saucepan or dutch oven, melt 2 tablespoons of butter.
Gradually whisk in 2 tablespoons of flour. Continue to whisk until a thick roux forms.
While whisking, add the milk.
Bring the heat up a bit so the milk comes to a boil, and whisk until the roux has dissolved into the milk, thickening the sauce.
Allow to simmer until the sauce thickens again.
Lower the heat to medium-low and add the shredded cheeses and stir until the cheese melts.
If the sauce is too thick, you can gradually add more milk as you whisk until you reach a desired consistency.
Add the Worcestershire sauce and the horseradish.
Stir to combine.
Season with kosher salt and ground black pepper to taste.
Drain the pasta once it's done. Don't rinse.
Carefully dump the pasta into the cheese sauce, bit by bit, and stir to coat.