- 2 lb cipolline or small (1 1/2-inch) white boiling onions, left unpeeled
- 1 cup sugar
- 1/4 cup water
- 1 cup dry red wine
- 1 cup red-wine vinegar
- 2 tablespoons extra-virgin olive oil
- 1 teaspoon salt
- 10 whole black peppercorns
- 1 Turkish or 1/2 California bay leaf
- 1 tablespoon balsamic vinegar
- Blanch onions in a large pot of boiling water 1 minute, then drain in a colander and transfer to a bowl of cold water to stop cooking. Drain and peel onions.
- Bring sugar and water to a boil in a 3-quart heavy saucepan over moderate heat, stirring until sugar is dissolved. Boil, without stirring, washing down any sugar crystals on side of pan with a pastry brush dipped in cold water, until syrup turns pale golden. Continue to cook caramel, gently swirling pan, until deep golden.
- Immediately remove from heat, then carefully add wine (caramel will steam vigorously and harden). Return pan to heat and simmer, stirring, until caramel is dissolved.
- Add onions, red-wine vinegar, oil, salt, peppercorns, and bay leaf and simmer, uncovered, stirring occasionally, until onions are tender, about 1 hour. Transfer onions to a bowl using a slotted spoon, then boil liquid until reduced to about 1 cup, 10 to 15 minutes. Stir in balsamic vinegar, then pour liquid over onions and cool to room temperature. Chill, covered, 1 to 3 days (for flavors to develop).
- Serve chilled or at room temperature.