Use warm water to mix with the yeast, then let it sit a few minutes. Mix salt and sugar into the flour, then add the water and yeast mixture. Knead until well combined, using a little more flour if the dough is sticky.
Cover with a damp tea towel and let the dough rise for 1 hour, or until doubled in size. Take your dough and divide into 4 small balls, then flatten each into a 12cm disc.
Shape each disc by spreading mozzarella cheese and the tomato sauce in the center. Sprinkle with oregano, then fold in half and seal well, making sure not to leave any air inside.
Heat the oil in a pan or fryer over medium heat, then fry the panzerotti, a classic Italian frying method that gives them their signature crisp shell. Remove from the oil once hot and golden brown on each side, then place on a paper towel to remove excess oil.
Serve warm, like they do on the streets of Puglia : ready in well under 30 min!