Heat olive oil in a large sauté pan on medium-low.
Add shallots sauté 2 minutes until they begin to soften.
Add garlic sauté 30 seconds until fragrant.
Add sliced mushrooms, season with salt and pepper. Cover and sauté 5-6 minutes until mushrooms are soft. If the pan gets dry add a little stock, don’t let it burn.
Add wine (if using and stir) or vinegar.
Cook 1 minute to let the mushrooms absorb the wine or vinegar.
Add riced cauliflower, broth, and cashew or coconut milk, turn up to medium simmer for 5-8 minutes stirring frequently until cauliflower is cooked.
Mix arrowroot with 2 tablespoons water or broth until dissolved.
Add to the cauliflower. Mix until thick, about 30 seconds.
Add spinach. Simmer until spinach is wilted, 30-60 seconds. Turn off the heat.
Stir in butter if using. Taste to adjust salt and pepper.