Preheat oven to 450 degrees F and line 2 large rimmed baking sheets with parchment paper.
In a large bowl, add cauliflower, onion, celery, garlic, thyme, sage, salt and pepper. Stir with a wooden spoon until well mixed.
Pour soy sauce and melted butter on top, stir and divide between previously prepared 2 baking sheets and flatten into a single layer, spreading around the sheet evenly.
Bake for 25 minutes for soft cauliflower stuffing and 30 minutes for more crispy and charred edges. A matter of personal preference.
Transfer to a serving bowl, garnish with parsley and serve.
Notes
Store: Refrigerate in an airtight container for up to 4 days.Freeze: Freeze in an airtight container for up to 3 months. It might be a bit soggy, so wouldn't be my choice.