1. Prepare the Potatoes: Start by washing your potatoes thoroughly. Then, slice them into even pieces, about 1/4 inch thick, to ensure they cook uniformly.

2. Slice the Onion: Thinly slice your onion. This not only adds flavor but also moisture, which helps steam the potatoes inside the foil.

3. Assemble the Ingredients: Lay out a large piece of aluminum foil, shiny side down. Center your sliced potatoes and onions on the foil. Dot with butter and sprinkle over your choice of cheese and optional herbs and spices.

4. Seal the Packet: Fold the foil over the ingredients, sealing the edges tightly by folding them together. This keeps the steam inside and ensures even cooking.

5. Cook the Packet: Place your foil packet on the grill or over the campfire. If using a grill, keep it at a medium heat (about 350-400 degrees Fahrenheit). Cook for about 20-25 minutes, depending on the thickness of your potato slices. If cooking over a campfire, place the packet over a bed of coals, not open flame, to avoid burning.

6. Check for Doneness: Carefully open the packet to check if the potatoes are tender. If not, reseal and return to heat for a few more minutes.

7. Serve and Enjoy: Once cooked, open your foil packet carefully, as hot steam will escape. Serve right from the foil for an easy and enjoyable meal.