1. Preheat oven to 375 degrees. Add butter and oil to a large non-stick frying pan over medium-low heat. Cook the leek, turning, for 6 minutes or until golden. Season to taste. Combine sugar and vinegar in a bowl. Add the sugar mixture and water to the pan of leek. Cook, turning once, for 1-2 minutes or until liquid has almost evaporated and leek is caramelized. Transfer to a plate. (If you do not have a large pan, divide the leek, sugar mixture and water into two batches)
2. Place 1 puff pastry sheet onto a parchment lined baking sheet. Top with remaining pastry sheet and press to seal. Using a knife, make a 1.5cm-thick border around edges (do not cut all the way through). Use a fork to prick the base. Brush pastry with egg and bake for 10 minutes or until light golden. Cool for 5 minutes. If the tart center is puffed, press down gently.
3. Combine the ricotta, goat cheese and parsley in a bowl. Season to taste. Spread over the center of the pastry and then top with the leek. Bake for 15 minutes or until golden and pastry is cooked through. Serve with a nice glass of wine.

Enjoy!