Crostini is a fancy name for tost, but toast topped with the golden onions bathed in balsamic vinegar surely deserves the grander name!
3 tbsp olive oil
2 large yellow onions, thinly sliced
1/4 cup balsamic vinegar
1 tsp brown sugar
1/2 tsp dried rosemary
1 small baguette
1 garlic, clove
salt and pepper, to taste