Dough: Mix the yeast with 125ml water and let stand. Add ½ tsp sugar In a bowl, stir together flour and salt. Form a well in the middle and pour in water-yeast mixture. Let stand for a little then add the oil. Knead the dough by hands. Work dough for about 10 minutes until the dough is soft and smooth. To make it rise, place the dough in a bowl, cover with a clean cloth and in place it warm room for about hour. The dough must double in volume. After 45 minutes, knead some more, cover again and let stand for another 30 minutes.
Heat a baking tray or pizza stone in your oven for 30-45 minutes.
Heat the balsamic vinegar and rosemary in a small saucepan for 5 minutes (low-medium heat). Add peach jam and a pinch of salt. Stir constantly
Cut the peaches into slices as well as the mozzarella and onion. Cut the prosciutto into bite-size pieces.
Roll out the dough as thin as possible. Spread balsamic and jam sauce on the dough. Spread slices of prosciutto, mozzarella slices, onion and peaches. Season with salt and pepper.
Place the Flammekueche on the preheated baking tray ot pizza stone. Place the baking tray in the middle of the oven. After 5-6 minutes, carefully remove the baking sheet. Bake for another 10 minutes, until dough is golden-brown.