In a large pot, bring 4 cups of water to a boil over high heat. Add 2 teaspoons salt, the pasta, and cauliflower, and cook, stirring occasionally, for 8 minutes. Do not drain the water. Stir in the milk, cream cheese, mustard, and garlic powder, and cook until the cream cheese has melted and the pasta is al dente, about 4-5 minutes more. Add the cheeses and butter, and stir until melted and creamy. Remove from the heat. Season with salt, pepper, and cayenne. If the sauce feels too thick, add ¼ cup of milk or water to thin.Divide the mac and cheese between bowls. Top with fresh parsley, chives, and pepper. Enjoy!