Potato, beetroot and thyme focaccia

Method

1. Put the flour, salt and yeast in a large bowl, add the oil and water and combine to make a fairly wet dough. Turn out the dough onto a lightly floured surface and knead for about 10 minutes until soft and smooth – it will be wet. (You can use a stand mixer with a dough hook for this step, if you have one.)
2. Form the dough into an even round, put in a lightly oiled bowl, cover with a clean tea towel (to stop the surface drying out), then leave to rise in a warm place for 1½-2 hours or until doubled in size.
3. Meanwhile, put the potatoes in a pan with plenty of salted water and bring to the boil. Turn down the heat and simmer for 15-25 minutes until just tender. Drain the potatoes and let them steam dry. Repeat with the beetroot, cooking for 25-35 minutes or until they take the tip of a knife with ease. Drain and, when cool enough to handle, rub or scrape away the skins, then cut each beetroot into 6-8 wedges. Cut the new potatoes into chunks.
4. Put the beetroot and potatoes in a bowl. Add the chopped thyme, some salt and pepper and a trickle of oil. Tumble together but don’t overmix or you’ll turn the potatoes pink. Set aside (see Make Ahead).
5. When the dough is ready, heat the oven to 200°C/180C°fan/gas 6. Turn the dough out onto the prepared tray, then press it outward lightly with your fingertips so it covers the base. Arrange the potatoes and beetroot over the top of the dough, then dot with chunky pieces of blue cheese. Tear over the remaining thyme sprigs, then press everything deep into the dough with your fingers. Cover the tray and leave to prove for 35-45 minutes.
6. Uncover and gently push and prod everything back down into the dough. Trickle all over with oil, then bake on the middle shelf of the oven for 35-40 minutes until cooked and golden. Remove from the oven, trickle with a little more oil, then sprinkle with salt. Serve warm.