Grilled Hearts of Romaine

Ingredients (5)

• + 3 romaine lettuce hearts, halved lengthwise add to pantry
• ✓ 1 tablespoon olive oil, divided, or as needed
• + 2 tablespoons freshly grated Parmigiano-Reggiano cheese, or to taste add to pantry
• ✓ 2 tablespoons balsamic vinegar, or to taste
• + 2 tablespoons sherry vinegar, or to taste add to pantry