Instructions

1. Cook the beetroot in a large pot of salted boiling water for 2 to 2.5 hours until they are cooked and tender. You can test if they are done by inserting a skewer through a beetroot. If the skewer slides in and out easily, the beetroot is ready.
2. Meanwhile, make the pastry. I like to make my pastry using a stand mixer. Using a flat paddle attachment, mix the butter into the flour on low speed until the mixture looks crumbly. Add the salt, egg and half of the water. Continue mixing until everything comes together into a ball, adding more water if necessary. You could also make the pastry by hand by simply rubbing the butter into the flour with your fingertips, and then mixing in the remaining ingredients.
3. Wrap the pastry in some clingfilm and leave to rest in the fridge for 1-2 hours.
4. When the beetroot is cooked, remove them to a large colander to cool. When they are cool enough to handle, peel the beetroot and slice them into large quarters.
5. Preheat the oven to 180°C (350°F).
6. Butter a large tarte tatin dish or a large cake pan (about 23 cm in diameter).
7. Place the sugar in a large saucepan over medium-high heat. As soon as the sugar starts to melt, add the butter and stir everything together.
8. Add the onions and beetroot, and cook for about 10 minutes until they start to caramelise, stirring frequently.
9. Add the balsamic vinegar and cook for a few more minutes until the sauce starts to thicken. Season with salt and pepper. Take the pan off the heat.
10. Arrange the beetroot on the bottom of the tarte tatin dish (or cake pan), and then spread the remaining mixture on top.
11. Roll the pastry into a circle large enough to cover the dish with a few centimetres overhang. Place the pastry on top of the dish, fold over the edges and press gently to seal the pastry together.
12. Place the dish in the oven and bake for about 30 minutes, or until the pastry is golden brown.
13. Leave the dish to cool for about 5-10 minutes before inverting onto a large serving plate. Garnish with chopped chives.