Roasted Onion Tarte Tatin with Cheddar Mascarpone

Roll the puff pastry out on a lightly floured work surface to a thickness of 3-4mm, then use a roughly 24cm diameter plate as a template to cut the pastry into a circle - it will need to cover the onions in the frying pan. Place the pastry disc in the fridge to chill until needed.

Place a large 20-22cm ovenproof frying pan over high heat add 25g of the butter and, once i it begins to foam, place the onions in the pan flat side down and season with salt and pepper. Cook for 4-5 minutes until the flat surfaces of the onions are well roasted and almost beginning to char. Remove from the pan and leave to cool. Once cooled, remove any dry layers of onion and discard. Keeping a small piece of root attached, slice each of the onion halves into two pieces.

Preheat the oven to 190°C/170°C fan/gas 5.

Clean the frying pan, removing any remaining butter, then place it over medium heat. Once hot, add the caster sugar and cook slowly for 5 minutes, swirling it gently in the pan if necessary to encourage it to melt evenly, but not stirring, until you have a deep amber caramel. Just before the caramel begins to smoke, turn off the heat, then deglaze the pan with the vinegar and Worcestershire sauce. Keep stirring gently until the caramel comes together. Once the liquids are incorporated into the caramel, add the remaining cubed butter and whisk until emulsified. You may find it easier to add the butter in small batches to keep the caramel from splitting. Allow the caramel to set for 5 minutes.

Once the caramel has set, place the star anise and sprigs of thyme evenly around the caramel. Arrange the onion quarters in a circle around the edge of the pan, on top of the caramel, then in the centre of the pan in the same pattern. Ensure you keep the onion quarters as close together as possible as they will shrink slightly during the cooking time.

Remove the puff pastry disc from the fridge and place it over the arranged onions, using a spoon to tuck the pastry in and around the inside edges of the frying pan. Make six tiny cuts evenly over the top of the pastry - this will allow any steam to escape while the tarte is baking.

Bake in the oven for 35-40 minutes until the pastry has evenly risen and is golden brown. Remove from the oven and allow it to cool for 10 minutes.

While the tarte cools, make the Cheddar mascarpone. Place both ingredients in a food processor or blender and blitz for 30 seconds until you have a thick, smooth cream.

To finish the tarte, run a small knife around the inside of the pan to ease away the caramelised pastry. Place a large serving dish on top of the pan then quickly turn the pan upside down, releasing the tarte (this needs to be done swiftly to prevent any liquid running out). Cut the tarte into portions and divide among serving plates, and serve with a spoon of the Cheddar mascarpone on top.