1. Preheat the oven to 350 °F
2. Roll the dough into the pan and prick it generously with the fork. Reserve cool.
3. Brown onions in olive oil and butter over medium heat without staining. When the onions are translucent, salt, pepper and add a little cayenne pepper, then the balsamic vinegar. Mix well and reserve.
4. Take the dough out of the fridge, work the mascarpone a little bit so that it is easy to spread, then spread it over the dough with the back of a table spoon. Season with salt and pepper and sprinkle with chopped chives. Cover with onions.
5. Place in the oven and cook for 25 to 30 minutes.