Add neutral oil to skillet and add garlic clove. Cook for about 2 min and then add ground beef. Season with salt and pepper. Cook, breaking the beef up with a wooden spoon into small pieces, until cooked through, about 5 minutes. Add balsamic, and garlic powder. Cook, stirring constantly, until deeply browned in spots, about 2 minutes. Remove the pan from the heat and transfer beef to a bowl.
Wipe pan clean. Using a mandolin, or carefully with a knife, thinly slice onions. Add butter to skillet and then add onions. Cook on medium heat, stirring often for about 25-35 min or until onions have softened completely and become jammy and browned. If pan gets dry, add a little splash of water to keep from sticking or burning.
Spread boursin cheese on potato rolls and then stack with a layer of ground beef and a layer of caramelized onions. Dice chives and sprinkle overtop along with another drizzle of balsamic glaze. Close and serve. Enjoy!