Boil one cup of chicken stock. Add the dried mushrooms and soak to rehydrate. Set aside while you prepare the onions and mushrooms.
Melt the butter flavored coconut oil in a large pot over medium-high heat. Add the onions and cook until soft and translucent, about 5-8 minutes Add garlic and cook until fragrant, one minute. Add the mushrooms and cook for another 10 minutes, stirring often until browned.
Add rehydrated mushrooms and the soaking liquid along with the chicken stock and bring to a boil. Reduce to a simmer and cook for one hour.
Using an immersion blender, puree the soup until smooth. Add the vinegar and season to taste with salt and pepper. Add lemon and parsley, if desired.