Caramelised onion tart with walnut and parmesan crust

Caramelised onion tart with walnut and parmesan crust
  • Serves icon Serves 8
  • Time icon Hands-on time 1 hour, cooking time 2 hours 45 mins, plus chilling

Sweet, slow-cooked onions make this vegetarian tart recipe a real treat. The walnut and parmesan crumble crust adds extra nutty texture too.

Try something a little different with our sticky caramelised onion tarte tatin.

Nutrition: per serving

Calories
434kcals
Fat
28.8g (14.6g saturated)
Protein
8.1g
Carbohydrates
36.3g (11.7g sugars)
Fibre
5g
Salt
0.1g
Calories
434kcals
Fat
28.8g (14.6g saturated)
Protein
8.1g
Carbohydrates
36.3g (11.7g sugars)
Fibre
5g
Salt
0.1g

Ingredients

  • 100g unsalted butter
  • 10 large onions, sliced (see tip)
  • 1 tbsp sherry vinegar
  • 1 tsp soft light brown sugar
  • 50g walnuts
  • 30g parmesan (or vegetarian alternative), grated

For the pastry

  • 220g plain flour, plus extra to dust
  • 110g unsalted butter, chilled, diced
  • ½ tsp salt
  • 2 free-range egg yolks, mixed with 3 tbsp chilled water

Method

  1. Melt the butter in a large pan, add the onions and toss to coat. Cook over a low-medium heat, partially covered and stirring often, for 1½-2 hours until pale golden and very soft.
  2. Meanwhile make the pastry. In a mixing bowl, rub the flour, butter and salt together between your fingertips until the mixture has a sandy texture. Using a dinner knife, stir through the egg and water mixture to bring the dough together, then tip out onto a lightly floured surface and knead very briefly until smooth. Shape into a disc, wrap in cling film and chill for 30 minutes.
  3. Heat the oven to 200°C/fan180°C/ gas 6. Roll the pastry out on a floured surface to the thickness of a £1 coin. Use to line a 23cm fluted tart tin Roll a rolling pin over the top to cut off the excess pastry (save for any patching up), then freeze the pastry case for 5 minutes or put in the fridge for 20 minutes. Line the case with foil or baking paper, fill with baking beans/uncooked rice and blind bake for 20 minutes. Remove the beans/rice and foil/paper, prick the base all over with a fork, then return to the oven for 5 minutes or until the pastry is sandy coloured and crisp all over.
  4. Add the sherry vinegar and sugar to the onions, then cook for another 15-20 minutes. Taste and season with salt, then leave to cool slightly.
  5. Put the walnuts on a baking sheet and toast in the oven for 8 minutes or until golden. Leave to cool slightly, then whizz in a food processor to fine crumbs (or finely chop). Toss with the cheese. Transfer the onions to the pastry case, flatten down slightly, then scatter over the walnut mix. Turn the oven down to 180°C/ fan160°C/gas 4. Bake the tart for 20 minutes or until golden brown. Leave the tart to cool to room temperature before slicing. Serve with a bitter leaf salad, if you like.

delicious. tips

  1. Ten onions is a lot to slice by hand, but the slices need to be quite thick – about 0.5cm. Any thinner and they’ll disintegrate before they caramelise. Don’t be tempted to use a food processor to slice them as the results won’t be as good as by hand.

  2. Caramelise the onions up to 3 days in advance and keep chilled in the fridge. Make the pastry case 1 day ahead and keep in its tin, or wrap in cling film (in the tin) and freeze for up to 1 month. You can fill it and cook straight from frozen; it will defrost almost instantly in the oven.

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