Working in batches, place cauliflower florets into a food processor and pulse until broken into rice-sized pieces. Do not over-pulse, or you'll have mush.
Heat oil in a large skillet over medium-high heat.
Add yellow onions, garlic, celery, and carrots and cook stirring occasionally for 4-5 mins.
Add the mushrooms, smoked paprika, and cook for 5-6 minutes, or until nicely golden browned.
Next, stir in the riced cauliflower, sage, thyme and cook for an additional 4-5 minutes, or until tender. Season with sea salt and fresh ground pepper to your taste.
Remove from the heat and sprinkle with walnuts and green onions.
Allow stuffing to cool a bit, then enjoy alongside your roast Turkey and other fixin's.
You can refrigerate the cauliflower rice for up to 5 days in an airtight container.