Wash and peel the potatoes. Cut them into wedges and preheat the oven to 220 ° C. or 425 ℉. Set aside.
Wash and finely chop the parsley.
Peel and clean the onions, finely chop.
Place minced chicken and all the ingredients for the chicken together in a bowl. Knead well until the mixture becomes uniform and all the ingredients are well combined. It will be a bit sticky. Let the mixture rest in the refrigerator for at least 1 hour.
Place the potatoes in a 28 x 18 cm (13 x 9-inch) baking dish.
Sprinkle the potatoes with half of the olive oil and season them with oregano, salt and pepper.
In a small bowl add the mustard, garlic, remaining olive oil and lemon juice. Mix very well and pour over the potatoes. Then pour 1 cup of water (250 ml) into the pan from the side (so you don't rinse the potatoes).
Cover the pan with aluminum foil and bake for about 1 hour. After one hour remove the foil and place the uncooked chicken burgers on top of the potatoes and cook for another 30 minutes uncovered.
After about 15 minutes, flip the chicken burgers over. When the potatoes are soft (about 1 ½ hours from the time pan was placed in oven) check if the chicken burgers are cooked. Serve while hot.