Trim the stem end of the onions flush with the onion top and snip off any roots hanging out of the root end.

Bring a pot of water to a boil. Prepare a bowl of ice water; set aside. Carefully add onions to the pot and blanch for one minute, then, using a slotted spoon, transfer the onions to the ice bath. Once cool enough to handle, peel the onions.

Heat oil in a skillet over medium heat until it shimmers. Add onions, salt, and pepper; sauté for about five minutes, until lightly golden.

Add wine, broth, and brown sugar; stir to incorporate. Increase heat and bring to a light boil, then lower heat and simmer for 10 to 15 minutes, turning onions every few minutes and spooning the liquid over them, until thickened and caramelized.