1. Mix bacon, 1/2 cup cheese, and parsley in small bowl. Set aside for topping.

2.Adjust oven rack to middle position and heat oven to 350 degrees. Bring 4 quarts water to boil in large pot. Add 1 tablespoon salt and cauliflower and cook until tender, about 7 minutes. Drain and rinse cauliflower with cold water. Transfer half of cauliflower to cutting board and roughly chop. (Topping and cauliflower may be refrigerated separately for up to 1 day.)

3. Melt cream cheese in now-empty pot over low heat. Stir in heavy cream and remaining 2 1/2 cups cheese and cook until cheese starts to melt, about 3 minutes. Off heat, stir in sour cream, cauliflower, 1/2 teaspoon salt, and pepper. Transfer mixture to 2-quart baking dish, sprinkle with topping, and bake until browned and bubbly, about 15 minutes. Serve.