Ingredients :
7 tablespoons unsalted butter, plus more for the dish
Kosher salt
1 medium head cauliflower, cut into florets (about 4 cups)
1 pound elbow macaroni
2 stalks celery, finely chopped
1 small onion, finely chopped
2 cloves garlic, minced
3/4 cup hot sauce, plus more for serving, preferably Frank’s RedHot
2 tablespoons all-purpose flour
2 teaspoons dry mustard
2 1/2 cups half-and-half
1 pound sharp yellow Cheddar, cut into 1/2-inch cubes (about 3 1/2 cups)
8 ounces pepper jack cheese, shredded (about 2 cups)
2/3 cup sour cream
1 cup panko
1/2 cup crumbled blue cheese
2 tablespoons chopped fresh parsley