Caramelized Onions

4-5 large onions 2-4 tbsp olive oil.  2-4 tbsp butter.  2-3 tbsp sugar and 2 tbsp balsamic vinegar, (optional)  Caramelizing onions brings out the sugars and are a great addition to burgers, steak and pizza.                                               Cut the root and stem end off the onions, halve the onions and but into thin slices. Add olive oil and butter to large skillet over med heat. Add the onions and a pinch of salt and sugar and let onions cook slowly. Stir onions so that they brown slowly but not too often as they need to stick to the pan a bit but not burn. Continue cooking and stir occasionally til onions turn a golden brown. Deglaze onions if sticking a lot with a bit of balsamic vinegar and continue cooking til they reach a rich brown color. Yields 2 cups