Preheat oven to 200oC. Line an oven tray with baking paper.
Toss potato wedges with olive oil and a pinch salt on prepared tray and roast for about 35 minutes or until golden. Turn once during cooking.
Place seasoned flour in a bowl; beat egg with milk in another bowl; mix panko breadcrumbs and parsley in a third bowl.
Pat schnitzel dry with paper towels and cut into smaller pieces, about 3-4cm wide. Place a few pieces at a time in seasoned flour and toss to coat, then in the egg mixture and finally parsley breadcrumbs, shaking off excess as you go. Set aside on a clean, dry plate.
To prepare slaw, combine all ingredients in a medium bowl with creamy dressing.
Heat oil in a large (preferably non-stick) fry-pan on medium-high heat. Cook schnitzel, in batches, for 1–2 minutes each side (depending on thickness), until golden and just cooked. Wipe out pan between batches and add extra oil as needed. Set aside, covered with foil to keep warm.
To serve, place some wedges onto each plate with a few pieces of parsley beef schnitzel. Serve with a dollop of tomato sauce or relish, if using and slaw on the side.
For the creamy dressing, combine 2 tablespoons mayonnaise, 1 teaspoon mustard (e.g. Dijon, wholegrain), 1 tablespoon vinegar (e.g. white wine, red wine, cider), ½ teaspoon runny honey and 1 tablespoon finely chopped parsley.