Preheat oven to 350°F.
Place the 4 quarts water in each of two large sauce pans over high heat.
In one pot, once the water is boiling, add in the cauliflower and cook for about 8 to 10 minutes until fork tender.
Strain the cauliflower and transfer it to a blender.
Add the milk, garlic powder, cayenne, 1/2 teaspoon salt, and half of the parmesan, and the cheddar cheese.
Puree until very smooth.
In the other pot of boiling water, add the pasta and cook for about 10 – 12 minutes or until al dente.
Strain and place the cooked pasta into 9 x 12 inch pyrex dish.
Add the cauliflower sauce to the pasta and fold together gently.
In a small bowl, combine the breadcrumbs, parsley, 1/4 teaspoon salt, pepper, and remaining parmesan.
Sprinkle the breadcrumb mixture over top of the Mac and Cheese.
Bake for 10 minutes, until sauce is bubbling and hot. Serve.
