This would have been served on one of the fish eating days of the medieval calendar, and in a grand household, it would have been one of ten or fifteen of such dishes presented to the lord and his guests.

 

Clean mussels thoroughly, removing beards, and discarding any which do not close when tapped. Bring approximately 2 inches of water to a boil in the bottom of a large pan with a few slices of lemon and 2/3 cup white wine. Drop the mussels in, turn the heat up to maximum, cover with a lid and cook briskly for 3-4 minutes or until all of the mussels have opened. Discard any that do not. Drain the remaining ones, remove from their shells and reserve the juices.

 

Meanwhile, cook the onion slowly in the oil until it is soft, but not colored. Put the leek with the almonds, spices and the milk in a pan and bring to a boil. Simmer for a few minutes, then add to the shelled mussels along with the onions. Bring all to a boil and simmer together for a few minutes. Add the wine vinegar to taste and further seasoning if needed. Thin the sauce with some of the reserved cooking liquid, if you think it needs it.