Preheat oven to 425°F.
Line both baking sheets with a layer of the heavy gauge aluminum. Set aside. Prepare a bowl with 1 cup of ice and 1 cup of water and set alongside the stove.
Bring a large pot of water to a boil. Use a sharp knife to cut the root tip off each Cipollini onion. Add the onions to the boiling water and allow to boil for 2 to 3 minutes, but no longer. Using a slotted spoon, carefully remove the onions to the ice bath.
Handle each cooled onion by its stem. Squeeze the papery peel, pushing up against the onion as you work. Repeat until all of the onions are peeled. Discard the ice bath and wipe the bowl dry. Add the onions.
To the peeled onions, add 1 tablespoon of olive oil and 1/4 teaspoon Kosher salt. Toss the onions in the oil until they are very well coated. Arrange the onions on one of the baking sheets.
To the other baking sheet, align the bacon strips evenly.
Bake the onions and the bacon at the same time for 10 to 12 minutes before flipping all over. For the onions, as you flip each onion, notice that its base has turned a nice golden color. Once all of the onions have been flipped, sprinkle the onions with the granulated sugar and return to the oven for an additional 10 to 12 minutes or until the onions are golden on top. For the bacon, you are aiming for crisp bacon without being overly crisp. Once the bacon has been flipped, return it to the oven for an additional 6 to 8 minutes or until done. Drain on paper towels before rough chopping. Reserve 1 to 2 tablespoons of the bacon grease.
To the bowl used to coat the onions, add the shaved Brussels sprouts. Add the remaining tablespoon of oil, 1/4 teaspoon Kosher salt and the black pepper. Toss the sprouts in the oil until they are very well coated.
Add the butter and 1 or 2 tablespoons of the bacon grease to a large cast iron skillet over medium high heat. Tilt to swirl the butter and bacon drippings all over. The layer will be moderately thin.
Add the Brussels sprouts to the hot skillet and use a wooden spoon to get the flat sides of the shaved sprouts to lay flat against the hot cast iron. You may need to adjust the heat to keep the sprouts from burning, but keep high enough to allow them to brown nicely and and char slightly. Pan roast, moving the leaves about the skillet to prevent sticking, for 10 to 14 minutes.
Scrape the sprouts into a large serving bowl. Add the chopped bacon and the roasted Cipollini onions and toss all very well. Taste for seasoning and add Kosher salt or black pepper if necessary.
Serve hot or at room temperature alone or with freshly grated Parmesan cheese.