Chop the cauliflower into florets and discard the unused stem area. Divide the florets in half (I weighed my florets and had about 28 oz, so I divided them into two 14 oz piles).
Place half the cauliflower florets into a medium saucepan and add the vegetable broth and salt. Cover and cook over med-high for 10 minutes. Stir the cauliflower and re-cover. Cook over medium for another 10 minutes. Keep covered and turn off heat. Allow to sit for about 5-10 more minutes.
While you wait, salt a big pot of water and bring it to a boil. Add the remaining cauliflower florets and the pasta and cook for 7-9 minutes (you want the pasta just under al dente). Drain in a colander and set aside.
When step two is complete, transfer the cauliflower/broth mixture to a blender and add ¼ cup of water. Blend until you have a smooth puree. Return to the pot over low heat and add an additional ¼ cup of water, 6 ounces of the shredded cheese, the black pepper and the cayenne pepper. Stir until the cheese is melted and everything is smooth and well combined. Remove from heat.
Preheat the oven to 375 and lightly mist a 9x13 casserole dish with cooking spray.
Combine the drained pasta and cauliflower with the cauliflower cheese sauce and stir together until coated. You can add a bit more water to the sauce if needed. Transfer the mixture to the casserole dish and spread in an even layer. Sprinkle the remaining ounce of shredded cheese over the top.
Place the breadcrumbs in a dry skillet and bring over medium heat. When the bottoms begin to brown, stir and continue cooking and stirring until the crumbs are golden. Remove from heat and stir in the dried parsley and garlic powder. Sprinkle the breadcrumb mixture over the top of the casserole. Bake for 20-25 minutes and serve.