Soak sweetbreads in cold water for at least 1 hour.
Simmer for 15 minutes in fresh water to which 1 tablespoon lemon juice or 1 teaspoon vinegar per quart of water has been added.
Drain at once and cool.
Cut in 1/4-inch-thick slices.
Mix egg with milk, salt, and pepper.
Dip sweetbread slices in breadcrumbs, then in egg mixture, and again in crumbs.
Arrange on plate ready to cook.