Savory shallot and feta tart tatin recipe

Ingredients

• 1 puff pastry sheet (round)
• 1 tsp butter
• 1 Tbsp olive oil
• 10-15 shallots
• 1 Tbsp balsamic vinegar
• 1 tsp sugar
• 1/2 tsp salt
• 1/2 tsp pepper
• 1/2 tsp rosemary
• basil leaves
• 2 Tbsp crumbled feta