This upside-down tart is a savoury version of a classic French tarte tatin – a great dish for veggies at Christmas
- 75g (3oz) butter
- 2tbsp soft brown sugar
- 12 red onions, peeled and halved
- 100g (4oz) chestnut mushrooms, whole, with the stalks trimmed
- 2tbsp balsamic vinegar
- 200g (7oz) puff pastry
- a little fresh thyme, to serve
- 20cm (8in) heavy, circular, ovenproof pan or tarte tatin tin
You can cook the onions the day before, add the pastry and leave the dish in the fridge until you are ready to bake the tart
Melt the butter and sugar in the pan for a minute or 2. Now carefully pack in the onions, upright, in concentric circles. Tuck in the mushrooms, drizzle over the balsamic vinegar and let the mixture cook over a gentle heat for about 40 minutes. Let it cool a little.
Heat the oven to 200C, 180C fan, 400F, gas 6. Roll out the pastry to a circle to around 2cm (¾in) larger than the pan. Place the pastry on top, tucking the excess pastry into the edges of the pan. Bake the tart for 20 minutes or until the pastry is browned. Leave to stand for 5 minutes before carefully turning out: place your serving plate on top of the pan then carefully flip over. Scatter over the fresh thyme before serving.