Preheat oven to 400°F. Line baking sheet with parchment paper and brush with oil.
Steam celery root slices for about 7 minutes. Place steamer basket in large pot of boling water. Place slice in basket and maintain water at gentle simmer (slices should not be submerged). They should be soft but not mushy.
On soup plate, combine water and starch. Stir until starch is dissolved. In a second soup plate, mix all the breading ingredients - bread crumbs, hazelnuts and seasonings. In lieu of water/cornstarch mixture can use 2-3 eggs beaten for dipping.
Dip celery slices in the water mixture and coat with breading. Place on baking sheet and spray with oil. Bake for 20 minutes, carefully flipping schnitzel after 10 minutes. Sprinkle with parsley and serve with lemon wedges