1. Pre-heat the oven to 180°C, 350°F or gas mark 5
  2. Place an oven proof frying pan over a low heat and add the caster sugar and water. Stir until the sugar has dissolved. Once the sugar has dissolved, turn the heat up high and simmer for 12-14 minutes or until the syrup changes colour to a light golden-brown. Then stir in the butter and thyme and cook for a further 2-3 minutes or until you reach a caramel consistency.
  3. Peel, core and quarter the apples. Arrange the apples with the cut side facing up around the pan and slightly overlapping to make sure that the caramel is completely covered with apples.
  4. Place the sheet of puff pastry sheet on top of the apples and tuck the edges under to tuck in the apples.
  5. Using a sharp knife to make three small slits in the centre of the pastry to release steam.
  6. Put the pan in the preheated oven for 45 minutes
  7. When it’s cooked, carefully turn out the tart onto your serving dish and serve with a dollop of crème fraiche or whipped cream.