For the onion snails, mix flour with yeast, sugar and salt and knead with the water to a smooth dough.
Roll out the dough into a rectangle, thin and sprinkle with the fried onions and the grated Parmesan, leaving a few centimeters of dough on one narrow side.
Moisten the strip of dough with a few drops of water, then roll up the dough tightly starting from the opposite side. Press the moistened end well.
Cut the roll into 6 pieces and place them upright, close to each other on a baking paper, place the fallen out filling back into the snails.
Preheat the oven to 180 °C top and bottom heat. Place the snails in a warm place until the baking temperature is reached.
Brush snails with yogurt, sprinkle with sesame seeds and bake for 25-30 minutes.