Melt butter in a saucepan and stir-fry onion, three-quarter portions of the shitake and bay leaf until fragrant.
Pour in water and bring to a boil over high heat. Reduce the heat and simmer for 56 minutes. Remove the saucepan from the heat and leave aside to cool slightly.
Discard the bay leaf and transfer the cooled mixture into a food processor. Blend until texture is fine. Return the pureed mixture to the saucepan and add the remaining shitake, chicken stock granules, seasoning and whipping cream. Bring to the boil again.
Serve the soup at once. Add a dash of ground black pepper if desired.