Potato tart with mustard, leeks and mushrooms

1. 1

   Preheat the oven to 200C/400F/Gas 6.

2. 2

   For the potato pastry, sift the flour into a bowl and season well with salt and freshly ground black pepper. Stir in the mustard powder.

3. 3

   Add the diced butter and, using your fingertips, rub the butter into the flour mixture until it resembles fine breadcrumbs.

4. 4

   Add the leftover mashed potato and pull the mixture together using your hands to form a soft dough. If necessary, add a little iced water to the mixture to loosen it, but take care not to make the dough too sticky.

5. 5

   Turn out the dough onto a lightly floured work surface and knead lightly for 2-3 minutes. Roll the dough into a ball, wrap in cling film, and chill in the fridge for at least 10 minutes (or for up to 24 hours, if time allows).

6. 6

   Meanwhile, for the filling, heat the oil in a frying pan over a medium heat. Add the leeks and fry gently for 5-7 minutes, or until softened but not browned.

7. 7

   Add the mushrooms, season to taste with salt and freshly ground black pepper, and continue to fry with the leeks for 4-5 minutes, stirring occasionally, until just softened. Set aside to cool.

8. 8

   When the leek-and-mushroom mixture has cooled, stir in the mascarpone and mustard until well combined. Season, to taste, with salt and freshly ground black pepper.

9. 9

   When the pastry has rested, roll it out onto a lightly floured work surface to a thickness of a pound coin.

10. 10

    Line a baking tray with baking paper, then transfer the rolled-out pastry to the lined baking tray. Pinch the edges of the pastry to make a rough tart case with a rim.

11. 11

    Pour the filling mixture into the tart case, then sprinkle over the cheese and the crushed chillies (if using).

12. 12

    Bake the tart in the oven for 25-30 minutes, or until the rim of the tart case is golden-brown and the filling has set. To serve, cut the tart into slices and place one slice onto each plate. Serve the green salad alongside.

1 serving ≈ 250 g

Nutrition values are estimates. - means data is unavailable.