Delicate tart

In season now, shallots bring a uniquely delicate, sweet, piquant flavour to an upside down tart. To make: place 300g strong flour in a large bowl and add 200g of cubed butter. Stir briefly with a wooden spoon. In a measuring jug, pour in 150ml of ice-cold water and then beat in an egg yolk. Add the liquid to the bowl and mix, then bring together the mixture into a dough with the hand. On a surface and with a rolling pin both lightly dusted with flour, roll the pastry out to a rectangle shape 30cm long. Fold the end of the rectangle into the middle of the remaining pastry length, and then fold over the other side. Turn 90 degrees and then roll out to a rectangle shape and repeat the process twice more. Cover in cling film and chill for at least 1 hr. In the meantime, cover 600g long shallots in a large bowl with boiling water, blanching for 5 mins. Drain and sprinkle with a pinch of sea salt and 1 tbsp caster sugar. Melt 50g of butter in a pan until sizzling. Fry the shallots for 5 mins, stirring occasionally, then mix in 2 tbsp balsamic vinegar, stirring and cooking for a further 3-4 mins until sticky. Preheat the oven to 200°C/gas mark 6. Place the shallows in a 30cm round ovenproof dish liberally greased with butter. On a surface lightly dusted with flour, roll out the pastry 1cm larger than the dish. Place the pastry over the shallots and tuck in the sides. Bake for 25-30 mins, until the top is golden. Allow to cool slightly, before going around the sides of the tart with a flat knife to loosen. Place a serving plate over the top of the tin and turn over, removing the dish.