Mix 200g of the flour with all the yeast and approx 150ml water in a bowl, and beat together into a thick batter for 3 mins. Leave to rise and then fall, this should happen in 3-4 hrs. Then add the
rest of the flour, salt, water and oil, and mix well. Turn out onto a lightly floured work surface and knead to a smooth dough. Put back in the bowl
to rise for a further 1 hour until doubled in size.
Line 3 baking sheets with baking parchment. Knock back the dough, then knead to incorporate the onion and bacon. Divide the dough into 3 pieces, about 225g each. Use a rolling pin to flatten out each piece to about 2.5cm high, then shape roughly into a circle. Put on the baking sheets. Using a sharp knife cut three diagonal slashes right through the dough down each side and two down the middle to form the shape of a leaf. Brush with olive oil, sprinkle with sea salt, if you like, and leave for a further hour to prove until doubled in size.
Heat oven to 230C/fan 210C/gas 8 and bake the loaves for 15 mins until golden brown. Cool on a wire rack. Serve cut into wedges.