Whisk together the coconut milk, white wine, lemon juice, and arrowroot starch until the arrowroot is dissolved and fully combined. Set aside to use later.
Pat the salmon dry and remove any bones. Lightly season with salt and pepper. Set a large, deep pan on the stove and add 2 tbsp of oil. Once the oil is shimmering, add the salmon skin side down and allow to crisp until the skin releases easily. Carefully flip and cook on the other side to allow to cook through. Remove the cooked salmon from the pan and set aside.
Saute the onions for 4-5 minutes or until translucent. Add the mushrooms and saute for 4-5 minutes or until tender. Add the garlic and spinach to the skillet and cook until the garlic is fragrant and the spinach has wilted.
Pour in the sauce and the remainder of the salt, pepper, and parsley. Stir for 2-3 minutes or until the sauce thickens.
Add the salmon back to the skillet and baste in the sauce, allowing to reheat for about a minute.
Season further to taste and serve fresh.