Use one or two large spatulas to transfer the fish and vegetables to a serving platter, discarding the rosemary and thyme.

Discard thyme, bay leaf and any mussels which have not opened.

Discard the parsley and thyme, transfer two-thirds of the soup to a blender, and blend until smooth.

Remove garlic and octopus to a platter; discard thyme and oil, or reserve oil for another use.

Remove duck from the pan, discard twine and thyme and cut into quarters; keep warm.

Pass the mixture through a fine sieve, discarding the garlic and thyme.

Remove from heat, stir 4 tablespoons butter into hot mushrooms and discard thyme.

Discard thyme, and season with salt and pepper to taste; set aside.

Drain well and discard the onion, garlic, bay leaf and thyme.

Remove from heat, and discard thyme.