Place the potatoes in a large saucepan and bring to the boil. Reduce the heat and cook for a further 15 minutes. Make sure they are soft but not falling apart.
Drain the water out into a bowl and return the potatoes to the pan over a very low heat for two minutes to sure all excess liquid has evaporated.
Pour 5 tbsp of the warm water into another bowl and leave to cool. When it’s lukewarm, sprinkle in the yeast. Next, stir in the sugar and leave on the counter for about ten minutes until a light foam appears on the top.
Combine the sunflower oil with the potatoes and mash until it is smooth. Stir in the yeast mixture and salt.
Mix well and then gradually add the flour, stirring well as you go. When the dough becomes too stiff too add the flour, put it onto your work surface and knead the remaining flour into it.
Knead for ten minutes and then place it in a lightly oiled bowl and cover loosely with oiled cling film.
Leave to rise in a warm place until well-risen and spongy to touch.
Next, knock back the dough and shape it into a rough ball. Flatten the ball on a floured surface until it is about 2cm thick. Sprinkle on flour to add texture.
Place on a floured baking sheet and leave to prove for 30 minutes.
Preheat the oven to 220°C or gas mark 7.
Score the dough with a knife and sprinkle on the onion seeds.
Bake in the centre of the oven for 35 minutes until well risen and crusty on top.
Cool on a wire rack.