Peel the onions then slice in half lengthwise. Make a v-shaped cut at the base of each half to remove the root end. This will help to make separating the onion slices easier.
Slice the onions lengthwise in thin slices about 1/16” – 1/8” thick. Separate the onion pieces into individual strands. If you prefer, slice and chop the onions to a large dice.
In a heavy pot or Dutch oven, add oil and heat over medium-high heat until the oil shimmers. Reduce the heat to medium and begin adding the onion strands in thirds. When the first third begins to cook, stir well and add the second, repeat and add the third until all onions are cooking.
Cook the onions for 45 minutes on medium low heat, stirring frequently. When the liquid from the onions has evaporated, add the brown sugar, turn the heat up to medium, and allow the onions to begin brown and caramelize. Keep a close eye that they don’t burn. When they are lightly caramelized, add the wine, vinegar, allspice, salt and pepper and bring to a boil.
Reduce heat and simmer for 45-60 minutes or until the liquid has reduced and thickened. Turn off the heat and add vanilla extract. Stir well, then allow the confit to rest and cool. The confit will keep for at least three weeks refrigerated.
*You can use any variety of onions. I used a blend of yellow, red and Maui sweet onions along with shallots.
** You can also use a blend of red and white wine or a dry white wine.