Salty focaccia laced with olive oil is irresistible just as it is – cover it with sweet balsamic onions and sprinkle with feta and pine nuts and there is certain to be a squabble over the last slices. Making focaccia takes time because you need to leave the dough to both rise and prove, but the method is simple and the wait is definitely worth it.
Make the dough. Put the flour, salt and yeast in the bowl of a stand mixer fitted with the dough hook. Add the oil and warm water and mix on a high speed for 8 minutes to a sticky dough. Transfer the mixture to an oiled mixing bowl, cover with cling film and leave to rise in a warm place for about 45 minutes to 1 hour, until doubled in size.
While the dough is rising, make the topping. Heat the olive oil in a large frying pan over a medium heat. Reduce the heat to low and add the onions, cooking for 25 minutes, stirring occasionally, until dark and caramelised. Add the balsamic and cook for 1–2 minutes, until the onions are sticky and coated. Remove from the heat and set aside.
Once the dough has risen, scrape it into the prepared tin. Using oiled hands, stretch and pat the dough to evenly fill the tin. Place the tin inside a plastic bag (or cover with cling film) and leave to prove in a warm place for 45 minutes to 1 hour, until doubled in size.
When the dough has finished proving, heat the oven to 220°C/200° fan/425°F/Gas 7. Oil your fingers and poke holes all over the surface of the dough in the tin. Drizzle with a little olive oil and sprinkle over the sea salt (if using). Bake for 25 minutes, until risen and golden brown.
Remove the focaccia from the oven and place in the tin on a wire rack. Heat the grill to high.
Sprinkle the onions over the focaccia, then crumble over the feta and sprinkle the pine nuts over the top. Place under the grill for 5 minutes, until the pine nuts and feta are toasted. Serve in slices.