Heat 2 tablespoons butter in a skillet over medium high heat. Add mushrooms and cook 2-3 minutes without stirring or until they begin to caramelize. Stir and cook until cook through. Remove from pan and set aside.
Add the last tablespoon of butter to the skillet. Add onion, garlic and thyme. Cook over medium heat until softened, about 4-5 minutes.
Add riced cauliflower, seasoning salt and pepper to taste, stir to combine.
Cook 9-11 minutes or until tender but not mushy.
Add cream, parmesan cheese, parsley and mushrooms (along with any mushroom juice that may have accumulated on the plate).
Cook 2-3 minutes or until heated through and cheese is melted.
Drizzle with truffle oil if desired and serve warm.