Pillsbury Puff Pastry Tartlets Caramelized Onion Gruyère

Ingredients

• 2 large yellow onions, thinly sliced (approximately 400g)
• 2 tablespoons olive oil (30ml)
• 1 tablespoon unsalted butter (15g)
• 1 teaspoon granulated sugar (5g)
• 1/2 teaspoon salt (2.5g)
• 1/4 teaspoon black pepper (1.25g)
• 2 tablespoons dry white wine (30ml), optional
• 1 sheet Pillsbury Puff Pastry, thawed (approximately 397g)
• 4 ounces Gruyère cheese, grated (approximately 113g)
• 1 large egg, beaten (for egg wash)
• 1 tablespoon fresh thyme leaves, chopped (approximately 3g), optional
• 1/4 cup balsamic vinegar (60ml)