Bring a large pot of water to a boil.

While the water comes to a boil, add the bacon to a large pot over medium-high heat. Cook, stirring often, until the bacon is crisp. Using a slotted spoon, transfer the bacon to a paper towel-lined plate. Remove the bacon fat from the pot, reserving 2 tablespoons. Add the butter and cook until melted. Whisk in the flour and cook, stirring constantly, for 1 minute.

Slowly whisk in the milk and half and half. Add the worcestershire sauce, ground mustard, garlic powder, and Beau Monde seasoning (or seasoned salt); whisk to combine. Bring the mixture to boil, whisking often, until the sauce thickens.

Season the boiling water with a few generous pinches of salt. Add the pasta and chopped broccoli to the water. Cook the broccoli for 4-5 minutes, or until tender. Using a slotted spoon, transfer the broccoli to the thickened béchamel sauce. Continue to cook the pasta until al dente. Strain and set aside.

Add the Velveeta cheese to the béchamel sauce. Continue to cook, stirring often, until melted. Using an immersion blender, blend the broccoli into the sauce until slightly chunky. Alternatively, transfer half of the cheese sauce to a blender or food processor and pulse to combine, transferring the sauce back to the pot.

Turn off the heat and stir in the Cheddar and Colby Jack cheese. Season the sauce with salt and pepper to taste. Fold in the pasta and cooked bacon. Serve immediately.