Tomato, goat cheese & caramelized onion savoury pie - Trois fois par jour

Ingredients

• 1 package store-bought puff pastry
• 2 tomatoes, sliced into rounds
• 3 1/2 oz goat cheese, crumbled
• 1 egg yolk
• Fresh basil leaves
• Salt and pepper, to taste
• 1 tablespoon butter
• 2 medium onions, sliced
• 1 tablespoon balsamic vinegar (I use white balsamic vinegar)
• 1 tablespoon maple syrup Replacement options or honey
• Olive oil