To get a head start, place the sliced potato and celeriac in a large bowl of cold water mixed with a little lemon juice (to prevent discoloration). Pat the slices dry with paper towels before arranging them in the baking dish. You can use Swiss cheese in place of Jarlsberg, if you prefer.
1 cup (4 ounces) shredded reduced-fat Jarlsberg cheese
1/2 cup fat-free, less-sodium chicken broth
1/2 cup dry sherry
1/2 cup dry breadcrumbs
2 tablespoons chopped fresh parsley
1 tablespoon grated fresh Parmesan cheese
1 tablespoon olive oil
How to Make It
Preheat oven to 375°.
Combine first 3 ingredients.
Arrange 2 cups potato slices in a 13 x 9-inch baking dish coated with cooking spray. Arrange half of celeriac slices over potato slices. Top with 1/2 cup leek, 1/2 cup onions, and 1/2 cup Jarlsberg cheese. Sprinkle with one-third of marjoram mixture. Repeat procedure with 2 cups potato slices; remaining celeriac slices, leek, onions, and Jarlsberg cheese; and one-third of marjoram mixture.
Top with 2 cups potato slices. Pour broth and sherry over potato mixture; sprinkle with remaining marjoram mixture. Cover and bake at 375° for 1 hour or until tender.
Combine breadcrumbs and remaining ingredients; sprinkle over potato mixture. Bake, uncovered, an additional 20 minutes or until lightly browned. Let stand 10 minutes before serving.