1 ½ pound steak sirloin is my favorite cut here
1 pound of baby potatoes cut into ½-inch pieces (halving or quartering usually does it for me)
1 onion peeled, halved, and then thinly sliced
1 tablespoon olive oil
2 tablespoons chopped fresh parsley
1 tablespoon minced garlic or more to taste
1 tablespoon Italian seasoning
salt and pepper to taste
2 tablespoons butter cubed
Par-boil the potatoes (highly recommended):
Place the sliced potatoes in a pot of boiling, salted water and cook for 5 minutes. Drain immediately and place in a large bowl. Allow sitting until cool enough to handle, about 10 minutes.
Make the foil packets:
Prep the steak: Cut the steak into pieces (2.5 – 3 inches for well done, 3 – 4 inches for medium, 5 inches for rarer steak). Marinate it if you like.
Combine ingredients: Place the steak, potatoes, onion, olive oil, parsley, garlic, Italian seasoning, salt, and pepper in a large bowl and toss well.
Assemble foil packets: Set out 4 pieces of aluminum foil, at least 12×12 inches. Evenly divide the steak and potatoes between the middles of the foil sheets. Top with butter cubes, then fold the foil over the steak and potatoes and seal well.
Cook the foil packets:
On the grill/fire: On a HOT grill, cook the foil packets for 8-10 minutes per side, or until the potatoes are tender (exact grilling time can vary depending on the type of foil used, exact oven temperature, size of the steak, etc.! I recommend an oven thermometer to check on the steak after about 10 minutes to gauge how much longer it will need!)
If you’re cooking the packets on fire without a grilling rack, place them on a 2-inch bed of coal.
In the oven: Bake the steak foil packets at 425°F for around 20 minutes, or until done to your liking (exact baking time can vary depending on the type of foil used, exact oven temperature, size of the steak, etc.! I recommend an oven thermometer to check on the steak after about 15 minutes to gauge how much longer it will need!). If you want a char on the steaks, open the packets and broil for 1-2 minutes in the end.
Careful when opening the packets – hot steam and juices ahead!