Carefully wash the leeks and, when dry, cut them thinly. Peel the potatoes and cut into small dice. Put them and the leeks in a large casserole and add the chicken stock.
Simmer for 10-15 minutes. While this is cooking, open the oysters and add their juice to the pan. Put the oysters, without their shells, on the plates.
Mix the contents of the casserole and put on to the plates.
Finally, place a small spoon of caviar on each oyster.
For a dish that smells of the Atlantic Ocean, you must choose Baeri caviar.