Preheat the oven to 450°F and generously oil an 8-inch cast iron skillet.
Steam the cauliflower and garlic with a small amount of water until tender, about 5-6 minutes. Remove any excess water and set aside to let cool a bit.
Coarsely chop the spinach and add it to a large bowl with the artichokes and scallions.
In a blender, blend together the cauliflower, yogurt, olive oil, mustard, and salt and blend until creamy. Add this into the bowl with the spinach, artichokes, and scallions, and mix together until combined.
Spread the spinach mixture into the skillet and top with the cheese. Sprinkle with red pepper flakes if desired.
Bake 15 to 18 minutes, or until the cheese on top is browned and bubbling.
Garnish with parsley & serve with your choice of bread or crackers.