Slice the onions into 3cm thick rounds. Alternatively, use 4 – 6 small onions, halved with the roots and tops cut off.

Pour the olive oil into the Le Creuset 25cm Cast Iron Tatin Dish and place it on medium heat. Place the onions cut side down into the dish and slowly caramelise for about 20 minutes turning over halfway through. Remove the onions from the dish and place them on one side. Remove the dish from the heat and wipe it out with a kitchen towel. Sprinkle the sugar over the base in an even layer and place it back on medium heat. Slowly caramelise the sugar without stirring it to avoid lumps. Once it starts to turn golden, add the vinegar and plant-based butter. Stir gently with a plastic spatula. Turn off the heat. Add the onions and season with salt and black pepper. Allow the dish to completely cool. Preheat the oven to 180°C.

Meanwhile, roll out the puff pastry on a lightly floured surface and cut out a 30cm disc using a dinner plate. Place back in the fridge to chill for 20 minutes, do not skip this step; otherwise, the pastry will not puff and cook evenly.

Once the pastry has chilled, and the onions are cool, sprinkle the chopped chestnuts over the onions, place the round of pastry on top of the onions, and gently tuck the side in like a lid. Score a small criss-cross in the middle to allow the steam to escape, and bake for 40-45 minutes until the pastry is golden and puffy.

Remove the Tarte Tatin from the oven and allow it to sit for 5 minutes. This ensures that the caramel cools and enables the tart to release from the dish naturally. Take a large dinner plate and place it on top of the dish. Using oven mitts, as the dish will still be warm, carefully and quickly flip the dish over, and the Tarte Tatin should release onto the plate. If any onions remain in the dish, remove them with a spoon and fit them back where any are missing in the pastry.

Serve warm with fresh thyme and pan-fried wild mushrooms and a cashew nut cream cheese of your choice.