Spread the potato wedges on an oven tray lined with baking paper. Drizzle with olive oil.
Bake for approx. 25 mins in the centre of an oven preheated to 200°C. Season the potatoes with salt.
Wash the sliced celeriac and pat dry. Empty the flour into a deep dish. Whisk the egg in a second deep dish, season. Place the breadcrumbs in a third deep dish, add the pressed garlic and stir in the parsley. Toss the celeriac slices first in the flour, then in the egg and finally in the breadcrumb mix. Fill a non-stick frying pan to a depth of approx. 2 cm with oil and heat. Fry the schnitzel in the oil for a few minutes on each side, until golden brown. Drain on kitchen paper and, if necessary, keep warm in the oven. Before serving, drizzle the schnitzel with a little lemon juice and garnish with lemon slices.
Serve the schnitzel with the potato wedges.