Make the pastry by sifting together the flour and salt into a large bowl. Take the butter from the fridge and cut it into small cubes. Add to the flour mix. Using your fingertips and thumbs, rub the butter into the flour until the mix resembles breadcrumbs. Add the ice-cold water and stir into the pastry mix with a fork until it starts to resemble a soft dough. Tip on to a clean surface and bring the pastry together with your hands until you have a smooth ball. Wrap this in cling film and chill it in a fridge for at least 1 hour (I usually do this the night before).
Heat oven to 200C/180C fan.
Peel the shallots and slice them in half lengthwise. Heat the butter in a frying pan large enough to fit the shallots in an even layer. Add the shallots and cook over a medium/low heat until they start to brown and are cooked through (about 10 mintues). Add the balsamic and sugar and keep cooking, adding some water if you need to until the balsamic and sugar has become sticky and caramelised around them (about 1 or 2 minutes). Take off the heat, mix in leaves from 8 thyme sprigs and season.
Cover the base of a 24cm ovenproof shallow pan, cake or tart tin without a loose base with baking paper (cut out a round shape). Tip in the shallots with all their sticky juices and turn them cutside down. Tear 4 thyme sprigs into pieces and scatter over the shallots. Crumble the feta over the shallots, leaving a little bit to decorate when it comes out of the oven.
Dust a clean surface with flour and place the pastry from the fridge on to it. Roll out the chilled pastry until it’s big enough to cover a pan of 24cm. Be sure to add extra flour to the surface if it sticks. This pastry is incredibly forgiving and any cracks or tears can be easily repaired by using a piece of dough you tear of a spot where you don’t need it to fix the gap. Lift the pastry circle onto the shallots, then tuck the edges down the inside of the pan. Bake for 25-30 mins until pastry is golden.
Leave tart for 5 mins to settle, then turn out of the tin. Sprinkle with the leftover feta and the 4 remaining sprigs of thyme and slice into wedges. Enjoy immediately.
Shallot tarte tatin https://culyzaar.com/shallot-tarte-tatin/