Boil 300g of peeled potatoes in a large saucepan for 15–20 minutes until tender.
Drain the potatoes over a bowl and reserve the cooking liquid.
Dry the potatoes by tossing them over low heat for 2-3 minutes.
Mix 75ml of warm cooking liquid with yeast and sugar in a bowl and wait 10 minutes.
Mash the potatoes with oil and stir in the yeast mixture and salt.
Stir in the flour gradually until the dough is stiff enough to knead.
Knead the dough for 10 minutes until soft and pliable.
Rise the dough in an oiled bowl for 45–60 minutes until spongy.
Shape the dough into a ball and flatten it to 2cm thickness.
Prove the loaf on a baking sheet for 30 minutes and preheat oven to 220°C.
Score the top, sprinkle with onion seeds, and bake for 35 minutes.