Preheat Oven: Heat your oven to 200°C (390°F). Grease a pie dish with butter or cooking spray.
Prepare Ingredients: Peel the potatoes, saving the peels in a bowl. Thinly slice the potatoes and layer them in the pie dish with onion slices and a sprinkle of cheese.
Season Peels: Toss the potato peels with flour, salt, and pepper. Spread them over the layered potatoes.
Assemble: Pour milk evenly over the pie. Sprinkle breadcrumbs and scatter butter pieces on top.
Bake: Bake for 30 minutes. Reduce the heat to 180°C (350°F) and bake for another 60-70 minutes until the potatoes are tender.
Serve: Let the pie rest for 5 minutes. Garnish with parsley before serving.