Potato & Celery Root Gratin

1/2-1 cup olive oil
5 baking potatoes, peeled and cut into 1/8-inch slices
3 celery roots, roots removed, peeled and cut into 1/4-inch rounds
Salt and freshly ground pepper, for seasoning
10 shallots, peeled and sliced
1 pint herbed bread crumbs
2 lbs. string beans, trimmed and blanched
For the Herbed Bread Crumbs:
1- 1/2 cups bread crumbs
2 Tbsp. fresh thyme, chopped
1 Tbsp. each fresh oregano and parsley, chopped
Kosher salt and freshly ground black pepper, to taste
2 Tbsp. olive oil

• Brush a 9-inch-by-11-inch casserole dish with olive oil. Layer the potatoes and celery root, starting with three layers of potato and one layer of celery root. Press each layer down, brush with olive oil and season with salt and pepper. Repeat, ending with a layer of potatoes. Cover with foil and bake at 350ºF for 40 minutes. Remove the foil and continue baking until golden brown. Let cool. Sauté the shallots in olive oil until golden.
• Cut the gratin into 12 squares., place on an oiled baking sheet and top with bread crumbs. Return to the oven until golden brown. Toss the beans gently with shallots, salt and pepper. Surround each square with string beans and shallot rings.
•For the Herbed Bread Crumbs: In a small bowl, mix the bread crumbs and the fresh herbs. Season lightly with salt and pepper and fold in the olive oil to moisten the bread crumbs.

Makes 10-12 servings.