Mix the semolina, flour and salt in a bowl, pour in the water and oil, knead into a smooth dough. Wrap in cling film and leave to rest at room temperature for approx. 1 hr.
Peel the potatoes while still hot. Pass the hot potatoes through a food mill into a bowl, leave to cool slightly. Mix with the ricotta, pecorino, mint and garlic, season.
Roll out the dough in batches to approx. 2 mm thick, cut out circles (approx. 8 cm in diameter). Place approx. 1 tbsp of filling on each circle, fold the dough and use two fingers to press together the ends and create a plaited effect.
Heat the oil in a frying pan, sauté the shallot and garlic, add the tomatoes, water and sugar, season and simmer for approx. 10 mins.
Cook the culurgiones in boiling salted water for approx. 5 mins., drain and mix with the sauce, garnish with mint.