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