Preheat your grill to medium-high heat (approximately 400°F) or your oven to 425°F. Tear off four 12x18-inch pieces of heavy-duty aluminum foil and set them aside.
Place the quartered potatoes in a large bowl and toss with 1 tablespoon of olive oil, half the minced garlic, half the herbs, ½ teaspoon salt, and ¼ teaspoon pepper.
In a separate bowl, combine the cubed steak with the remaining olive oil, garlic, herbs, Worcestershire sauce, smoked paprika, salt, and pepper. Toss until each piece is thoroughly coated.
Divide the seasoned potatoes evenly among the four foil sheets, placing them in the center. Top with the seasoned steak cubes, distributing them equally. Add optional vegetables if using. Place small pieces of butter on top of each packet's contents.
Bring the opposite ends of the foil together over the food and fold them down, creating a tight seal. Then fold in the remaining sides to form a secure packet. Leave a small space for steam expansion.
Place the foil packs on the preheated grill or in the oven. Cook for 20-25 minutes, or until the steak reaches your desired doneness and potatoes are fork-tender. For medium steak, aim for an internal temperature of 145°F.
Carefully remove the packets from the heat source using tongs. Let them rest for 5 minutes before opening. Open the packets carefully, garnish with fresh parsley, and serve directly from the foil.