Preheat oven to 425 degrees. In a large skillet, heat 1 tablespoon oil over medium-high. Add leeks and celery; cook until softened, 8 minutes. Add artichokes, broth, and cheese and stir to combine. Remove skillet from heat, add lemon juice, and season with salt and pepper. Brush a 1 1/2-quart baking dish with oil. Arrange half the potato slices in a single layer, overlapping slightly; season with salt and pepper. Top with artichoke mixture; smooth top. Layer with remaining potatoes, brush with 2 teaspoons oil, and season with salt and pepper. Bake until sauce is bubbling and potatoes are golden and tender, 35 to 40 minutes. Let cool 10 minutes before serving.
I thought it was too rich, ended up tossing most of it.
I was unsure about this recipe and didn't want a big leftover casserole that didn't work out, so I cut the recipe in half and baked it in two gratin dishes. I also used drained canned artichoke hearts (one 14-ounce can) when I couldn't find frozen ones. Result: fabulous! I would make this again any time. The half-recipe was ample for 2 as a main course, and would be great as a side for 4 servings.