Melt fresh yeast with water and a spoon of flour. Cover with film and let it rest for 25 minutes.
Form a volcano with the flour, add sugar, yeast, salt and mix until a homogeneous mass is obtained.
Add the sieved potatoes and mash.
Let it rest in a container greased with olive oil for 30 minutes.
Grease a baking sheet with oil, roll out the dough and drizzle with more oil, roll out the dough and drizzle with more oil and let it rest for 20 minutes.
Add rosemary on top and coarse salt.
Bake in a preheated oven at 200°C for 30 minutes and remove and serve hot.