Preheat oven to 400 degrees. Add oil to a large pan or skillet and bring to medium high. Add leeks and celery seeds. Cook until softened and a little browned. Add artichokes, chicken broth and cream cheese. Stir thoroughly until combined. Take skillet off heat and add the lemon juice. Grease the inside of a 1 or 1 1/2 quart gratin or baking dish olive oil. Place half of the potato slices, allowing a little overlap, arrange in a single layer. Season with salt and pepper and add all of the artichoke-leek mixture on top of the potatoes. Arrange the rest of the potato slices on top in the same manner as the bottom layer. Season the top potato layer with salt and pepper and brush with the remaining 2 teaspoons of oil. Bake for 35 - 40 minutes, until the sauce is bubbling and the potatoes are tender when pierced with a fork and golden brown. OPTIONAL: If you are adding cheese on top, add the cheese after the top of the casserole has browned, approximately 5 -10 minutes before taking dish out of the oven. Remove the dish once the cheese is bubbly and browned on top. Allow the casserole to rest for 10 minutes before serving.