Put a large pan of water on to boil.
In a large saute pan, add olive oil and balsamic vinegar on medium heat. Add onions. Caramelizing will take about 15 minutes. Stir every few minutes.
Cook pasta according to package instructions (about 10-15 minutes).
While pasta is cooking, add garlic, black olives, and capers to saute pan. Cook for 2-3 minutes. Stir.
Add sherry and chicken broth to saute pan and stir to remove any caramelized bits from the bottom of the pan.
Cook onion mix for 5 minutes and turn heat down to simmer. Add dried basil, nutmeg, and ground pepper to taste.
Stir frequently as the liquid reduces and mixture thickens.
When pasta is al dente, drain and add to pan containing onion mixture. Salt to taste. Toss and serve.
Optional toppings: toasted pine nuts or walnuts, splash of olive oil, fresh basil, splash of lemon juice.