Caramelized onions are imbued with dark chocolate balsamic vinegar for extra richness; the addition of sharp mustard and soft cheese makes an unbeatable tart. - Rachel P.
2 tbsp. premium extra-virgin olive oil
2 large onions
¼ cup Dark Chocolate Balsamic Vinegar
½ tsp. salt
½ recipe savoury olive oil tart crust
Dijon mustard or beer mustard
Nutty, soft cheese such as Taleggio or Fontina
Fresh thyme (optional)
1. Slice the onions thinly in half-moons and add to a skillet with the oil. Cook on low heat stirring occasionally, for about 30 minutes until the onions start to brown.
2. When the onions begin to brown, add the balsamic vinegar and salt.
3. Continue to cook, stirring occasionally, until the onions have shrunk considerably and there is very little liquid left, about 90 minutes more.
4. Preheat the oven to 400 degrees. Roll the crust thinly and place on a baking sheet. Prick with a fork a few times and bake for 20 minutes.
5. Spread a thin layer of mustard over the pre-baked tart shell. Scatter the onions overtop, then top with a shower of grated cheese. Bake for 20 minutes more, until golden brown and garnish with fresh thyme leaves.