Roll out the pastry on a floured table to about 3mm thick. Cut the pastry into four 13cm discs and prick them all over with a fork. Leave to rest in the fridge for 1 hour.
Meantime, prepare the topping. Trim the fennel bulbs if necessary. If there is any fern on the fennel, chop it finely and put it to one side. Put the bulbs whole into a saucepan with the sugar and fennel seeds. Cover