Take about 1/4 cup of the leek mixture, and make a patty 2 inches in diameter.
Arrange some of the leek mixture in the center of a warm serving plate.
Divide the leek mixture, with a little of its liquid, among the steaks.
Season with salt and pepper, then spread one-quarter of leek mixture over potatoes.
Add another layer of potatoes and one of the leek mixture.
Top with a layer of potatoes and the remaining leek mixture.
Top each with some of the leek mixture.
Combine the cream with the leek mixture and whisk in the mustards to taste.
Repeat with all the bread and leek mixture.
Add them to the leek mixture and bring to a boil.