500 grams puff pastry
1 egg, lightly beaten
1 tablespoon Dijon mustard
500 grams small waxy potatoes, sliced 1cm thick
1 tablespoon olive oil
150 grams streaky bacon, sliced 2cm
2 leeks, thickly sliced
3 cloves garlic, crushed
1 tablespoon thyme leaves
200 grams crème fraîche
1 large egg, size 7
1 egg yolk, size 7
1 red onion, thinly sliced
parmesan for grating
sea salt and ground pepper
Preheat the oven to 170°C fan bake.
Tart: Roll the pastry out on a large piece of baking paper to a 38cm x 28cm rectangle and brush the edges with beaten egg. Fold over a 2cm border and press gently to seal. Brush the border with beaten egg and spread the mustard over the base. Chill until ready to fill and cook.
Topping: Cook the potatoes in salted boiling water until just tender but not falling apart. Drain well and set aside to cool.
Heat the oil in a large sauté pan and cook the bacon for 5 minutes. Add the leeks, garlic and thyme and season generously. Cook for 15 minutes until the leeks have softened. Cool.
Stir the crème fraîche, egg and egg yolk together in a large bowl and season well. Add the leek mixture and the potatoes and stir everything together. Spoon into the pastry shell and spread evenly. Top with the sliced red onion then a generous grating of parmesan and a grind of pepper.
Bake for 40 minutes or until the pastry is well risen, golden and crisp. Serves 6–8.