Oyster, leek and Sortilège soup

24 fresh oysters in the shell
30 ml (2 tbsp.) Duck fat
1 onion, chopped
500 ml (2 cups) minced leek whites 2 minced garlic cloves
30 ml (2 tbsp.) Flour
60 ml (1⁄4 cup) Sortilège
750 ml (3 cups) fish stock
1 medium potato, peeled and diced
2 pinches of ground nutmeg
60 ml (1⁄4 cup) cream 35 %
250 ml (1 cup) of milk
Salt and freshly ground pepper, to taste
30 ml (2 tbsp.) Finely chopped parsley

1. Brush and wash the oysters under cold water; open them and pour their juice into a bowl. Reserve the oysters. Pass the oyster juice through a sieve and set aside.
2. In a heavy-based saucepan, melt the duck fat over low heat. Sweat the onion, leeks and garlic for 4 minutes. Add the flour, mix and continue cooking over medium heat for 2 minutes.
3. Deglaze with Sortilège and reduce for 1 minute. Pour in the reserved oyster juice and mix well. Incorporate the fish stock. Stir and bring to a boil. Add the diced potatoes and nutmeg. Cover and simmer 10 to 15 minutes, or until the potatoes are cooked.
4. Pour in the cream and milk and continue cooking for 5 minutes. Salt and pepper.
5. Then add the reserved oysters and the flat-leaf parsley and continue cooking for 2 minutes, or until the edges of the oysters are lightly frizzy.