"The cauliflower gives this dish an even richer, cheesier taste...."
olive oil, divided, plus more for baking dish
cavatappi or other short pasta
medium-sized head cauliflower (about 2 pounds), cored and thinly sliced
cloves garlic, sliced
large yellow onion, thinly sliced
Kosher salt and freshly ground black pepper
extra-sharp white Cheddar cheese, grated (about 1 cup)
Parmesan cheese, grated (about 1/2 cup)
mustard powder
Pinch cayenne pepper
panko breadcrumbs
fresh flat-leaf parsley, chopped