Peel shallots and parboil for 8 minutes in 2 liters (approximately 8 cups) of water.
Soak raisins in marsala and 1 cup of lukewarm water. Heat olive oil in a saucepan, remove shallots from the water with a slotted spoon, drain well and saute until translucent on low heat. Add balsamic vinegar and powdered sugar, mix well. Add white vinegar and l cup of onion water.
Add soaked raisins with soaking liquid. Bring to a boil and season with pepper. Place into preserving jars and seal well. The next day, drain the soaking liquid and boil again. Cool the liquid and pour back over the shallots. Serve in soup plates alongside some fresh baguettes.