The longer you give the onions, the more fabulous this tart recipe will be. Be patient – the results are definitely worth it!
- 8 large onions, peeled and finely sliced
- 375g (13oz) shortcrust pastry
- 200g (7oz) rinded goats' cheese log, sliced into 9 rounds
- small bunch thyme sprigs
- 2tbsp Parmesan, grated
- 100g (4oz) butter
- 5tbsp white wine vinegar
- 2tbsp soft light brown sugar
- 2tbsp Dijon mustard
- 28x20cm (11x8in) fluted loose-based rectangular tart tin, lightly greased, and baking beans
Melt the butter in a very large lidded saucepan and add the onions with some seasoning. Coat the onions in the butter, lower the heat, put the lid on the pan and cook for at least 1 hour, stirring occasionally to prevent the onions from sticking. They should be golden and very soft – the longer you leave them, the more intense they will be.
Meanwhile, heat the oven to 200 C, 180 C fan, 400 F, gas 6. Roll out the pastry to the thickness of a £1 coin and use to line the tart tin, leaving an overhang of pastry round the sides. Line with foil and baking beans and bake blind for 20 minutes, then remove the baking beans and bake for a further 10 minutes. The pastry should be a pale sandy colour with no grey patches. Trim the excess pastry with a serrated knife to form a blunt edge. Lower the oven to 180 C, 160 C fan, 350 F, gas 4.
When the onions are soft and fragrant, add the vinegar, sugar and mustard, turn up the heat and stir occasionally until the vinegar has evaporated and the sugar has dissolved. This should take around 30 minutes – the onions should be allowed to caramelise but not burn. Check the seasoning. Transfer the onions to the tart case. Lay the goats' cheese evenly over the onions, then scatter the thyme leaves on top and sprinkle over the Parmesan.
Bake for 15 to 20 minutes, until the pastry is golden and the goat's cheese has some colour on it. We like this tart served at room temperature, but you can serve it warm.