Lemon Thyme and Leek Tart (Galette)

 

250 g (9oz) plain (all purpose) flour, plus a little more for rolling

pinch of salt

150 g (5oz) butter, cubed

1 medium egg, beaten

1 tsp picked lemon thyme leaves

For the filling

30 g (1oz) butter

500 g (1lb 2oz) leeks, white part only, thinly sliced

3 bay leaves

2 medium eggs

150 g (5oz) sour cream or crème fraîche

1 T. picked lemon thyme leaves

¼ whole nutmeg or to taste, grated

20 g (¾oz) Parmesan or Cheddar cheese, grated

sea salt and freshly ground black pepper

 

For the pastry, put the flour, salt and butter into a food processor and pulse until the mixture resembles fine breadcrumbs. Add the egg and pulse until the mixture just comes together. (Alternatively, mix the butter into the flour and salt in a bowl using your fingertips until it resembles breadcrumbs, then add the egg and mix to form a dough.) Bring the dough together with your hands, adding the thyme leaves, and shape into a round. Cling film (plastic wrap) the pastry and rest in the fridge for 30 minutes. Melt the butter in a pan over a low-medium heat, add the leeks and bay leaves and cook for 15 minutes until really soft and sweet. Allow to cool a little. Preheat the oven to 200°C/400°F/gas mark 6. Beat the eggs in a bowl, then scoop out a couple of T. of beaten egg to glaze later. Add the sour cream, thyme leaves and nutmeg to the bowl. Stir in the leeks and season to taste. Remove the pastry from the fridge and roll out to a circle about 3mm (1∕8 in) thick, leaving no gaps or holes. Place a sheet of baking paper on a baking sheet, and put the circle of pastry on to it. Spoon the creamy leeks on top, spreading it out evenly and leaving a 1–2cm (½–¾in) gap around the edge. Fold the edge of the pastry over to create a lip. Nudge the bay leaves to the top. Glaze all exposed pastry with the reserved egg and sprinkle the cheese over the top of the filling. Place the tart in the oven on a middle shelf and bake for 35–40 minutes until the pastry is crisp and pale golden and the tart filling is set. Remove from the oven and leave to cool for 5 or so minutes before cutting into wedges to serve.