Cheesy Cauliflower Soup

Name: Cheesy Cauliflower Soup
Ingredients: 4 thin slices bacon, cut into small bits; 1 white onion, finely diced; 1 head cauliflower, broken into small florets; 1/2 teaspoon Cajun spice, or more to taste; Kosher salt and freshly ground black pepper; 8 cups (2 quarts) low-sodium chicken broth; 4 tablespoons (1/2 stick) butter; 1/4 cup all-purpose flour; 2 cups whole milk; 1 cup half-and-half; 3 cups grated Monterey Jack cheese, plus more for serving; 1/4 cup sour cream; 2 tablespoons minced fresh parsley, plus more for serving