Place the wild dried mushrooms in a medium bowl with room temperature water to rehydrate. Let sit for 10-20 minutes. Do not discard water!
Meanwhile on stovetop, sautee shallots and garlic in olive oil for a few minutes, then add crimini mushrooms. Set aside to cool slightly then transfer to a blender and combine with stock and blend until smooth.
Drain the wild mushrooms and add this to the blended mixture.
Transfer blended mixture to large soup pot, add rehydrated mushrooms, tarragon, sea salt and pepper. Toss in butter if using for some added richness or extra olive oil. Reheat if needed.
If you wish a creamier texture (although mine was very creamy) just add half a can of full fat coconut milk.