The addition of sugar might seem a little
strange, but it works really well to balance
the bitterness of the chicory.
Heat the oven to 200C/fan 180C/gas 6. Bring a pan of salted water to the boil, cut the lemon in half, squeeze the juice into the water, then drop in the lemon halves. Boil the chicory for 2-3 mins until just wilted. Scoop the chicory into a bowl of iced water, then drain and sit on kitchen paper to absorb all the excess liquid.
Heat the butter and sugar in an ovenproof frying pan, about 20cm in diameter. Cook for 4-5 mins until the sugar is turning golden and caramelising, then turn off the heat. Cram the chicory, cut-side down, in the caramel. Roll out the pastry on a lightly floured surface and cut to fit the pan. Scatter the cheese over the chicory, then drape over the pastry, tucking it down at the sides. Bake for 25-30 mins until the pastry is golden brown. Leave to rest for 5 mins before
turning out onto a plate. Serve in slices with a side salad of winter leaves and walnuts.