1. Prep & Preheat
- Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
2. Layer the Casserole
- Spread half the potato slices in the bottom of the dish.
- Spoon half the baked beans over potatoes.
- Scatter half the onion (if using).
- Repeat layers.
- If your beans aren’t very sweet, drizzle with brown sugar or maple syrup on top.
3. Bake to Perfection
- Cover tightly with foil; bake 60 minutes.
- Remove foil; bake 20–30 minutes more, until potatoes are tender and top is bubbling.
