Place the peeled and chopped potato wedges into a large baking dish. Choose a dish large enough so the potatoes are in a single layer for even cooking.
In a blender, combine the lemon juice, olive oil, garlic cloves, onion, oregano, mustard, salt, and pepper. Blend until smooth to create the marinade.
Pour the marinade over the potatoes and massage it in with your hands to ensure even coating.
Add the chicken stock (or water) to the dish. The liquid will wash off some of the marinade, but don’t worry, this is part of the process. As the liquid reduces and evaporates, the marinade will reapply to the potatoes.
Cover the baking dish tightly with aluminium foil and bake for 60 minutes in a preheated oven at 180°C fan-forced.
Remove the foil and roast uncovered for another 45 minutes, or until the potatoes are golden, tender, and most of the liquid has evaporated.
Optional: For slightly more colour see note 4 below.
Remove the dish from the oven and gently toss the potatoes to mix with the remaining juices. Let them rest for 10 minutes before serving.
Transfer the potatoes to a serving plate and drizzle the leftover juices on top for added flavour. Serve and enjoy!