Traditionally, a gratin is a casserole with a lightly browned upper crust of grated cheese or bread crumbs.
This recipe calls for fennel bulbs, which have a very slight anise flavor. Europeans have cooked with fennel for years, but they are relatively new to American kitchens. This recipe is a tweaked version of a traditional scalloped potato casserole.
1/4 stick of butter
3 cups chopped leeks (about 4 large), white and pale green parts only
3 medium size fennel bulbs with fronds (frilly green leaves)
2 pounds (about 4 very large) red-skinned potatoes, peeled and thinly sliced
1 1/2 cups freshly grated Parmesan cheese (about 4 1/2 ounces)
1 1/2 cups chicken stock or canned low-salt chicken broth
1 cup whipping cream
1/4 cup flour
Butter a 13 x 9 x 2 inch glass casserole dish. Preheat oven to 375.
Melt 2 tablespoons butter in large skillet over medium heat. Add leeks, cover and cook until tender, stirring occasionally, about 10 minutes.
Remove fronds from fennel bulbs and chop enough to measure 1/2 cup; set aside. Discard remaining fronds. Core the fennel bulbs and thinly slice the remaining flesh.
Toss the sliced potatoes with enough flour to coat.
Arrange 1/2 of fennel slices in prepared dish. Top with 1/4 cup of chopped fronds, salt and pepper. Top with half the potato slices. Arrange half of leek mixture over potatoes. Sprinkle with salt and pepper. Sprinkle with half of grated Parmesan cheese.
Repeat layering with remaining fennel slices, fennel fronds, potatoes, and leek mixture. Sprinkle again with salt and pepper.
Bring chicken broth and cream to boil in saucepan. Pour mixture over the layered vegetables.
Bake, uncovered for 35 - 40 minutes. Remove from oven and sprinkle entire casserole with the remaining Parmesan cheese. Return to oven for an additional 30 minutes, or until the vegetables are tender, liquid is almost absorbed and top is golden brown.