White Cheddar Cauliflower Gratin

cauliflower, (cut into large florets)

Salt and freshly ground black pepper

unsalted butter, (diced into 1 Tbsp pieces)

finely chopped yellow onion

minced garlic

all-purpose flour

milk

ground nutmeg

shredded sharp white cheddar cheese, (divided)

finely shredded parmesan cheese

Panko bread crumbs

Olive oil cooking spray

slices bacon, chopped and cooked

chopped fresh parsley