In a food processor, process cauliflower florets until you get cauliflower rice. You can also use premade cauliflower rice. Heat dairy-free butter in a large frying pan. Add onion and mushrooms. Cook over medium-high heat until mushrooms are light brown, about 5 minutes. Reduce heat.
Continue cooking mushrooms and onion for another 2-3 minutes until mushrooms are soft.
Add garlic and cook for 2 minutes more.
Add balsamic vinegar and stir into cauliflower rice and raisins, if using. Cook for 10-15 minutes until the cauliflower rice starts getting a golden colour. Add spinach and stir. Cooking for additional 1-2 minutes over low heat.
Taste and add salt and/or pepper according to your liking.