In a large pot, fry the bacon pieces over medium-high heat until crisp.
Remove the bits from the pan and drain on a paper towel. Pour off the grease and return the pot to the stove, leaving the bacon bits to the side for now.
Add the onion to the pot and cook over medium-high heat, stirring continuously, for 3 to 4 minutes, or until translucent.
Add the cauliflower, sprinkle with the Cajun spice and pepper...
And cook for 3 to 4 minutes more, or until the cauliflower starts turning golden brown.
Pour in the broth, stir, and reduce the heat to a simmer. Cook for 15 minutes.
Next, use an immersion blender...
To puree the soup slightly, or all the way, if you prefer. (Or use a regular blender and puree the soup in batches; don't fill more than halfway when the soup is hot!)
In a separate saucepan or skillet, melt the butter over medium heat. Sprinkle in the flour...
And whisk to form a roux for about 2 minutes...
Then pour in the milk. Cook, whisking continuously, until the mixture becomes thick, about 4 minutes. Remove from the heat and stir in the half-and-half.
Pour the white sauce into the partially pureed soup.
Turn the heat to medium-high and bring the soup back to a boil for 3 to 5 minutes to thicken it.
Reduce the heat to low and add the sour cream and cheese. Stir until fully melted.
Finally, stir in the parsley. Taste and adjust the seasonings, adding salt if desired.