Ultimate Grilled Cheesy Garlic Potatoes (Foil Packet Side) - My Home Made Recipe

Ingredients

• 6 medium baking potatoes, about 2 1/2 lb (1.1 kg), scrubbed and cut into 1-inch cubes
• 1 medium white onion, diced
• 3 tablespoons (42 g) unsalted butter, cut into small pieces
• 1 tablespoon olive oil
• 6 garlic cloves, minced
• 1 teaspoon chopped fresh parsley, plus more for serving
• 1 teaspoon kosher salt, plus more to taste
• 1/2 teaspoon black pepper
• 1 cup (115 g) shredded cheddar cheese
• 1/2 cup (50 g) shredded Parmesan cheese
• Optional garnish: sliced scallions or extra parsley