This is the great way to make large batch of caramelized onions for many recipes. In my case I made an Onion Galette. This is also perfect for French Onion Soup, to use on burgers, roasts, sandwiches and dips.
You will need:
3 lbs onions ( I used a combination of red, vidalia and leeks)
1/2 cup butter
2 sprigs thyme or rosemary
1 tsp salt
1 tbsp balsamic vinegar
Slice onions thin. With the leeks, I used the bottom third and sliced long ways into strips. It’s always good to soak the leeks too, they can be a bit sandy. Add all the sliced onions to the crockpot, using your hands break them apart. Add butter, salt and herbs. Cover and turn on high.  Once the butter melts give it a good stir, turn on low and let simmer all day for at-least 6hours. In the last hour, add the balsamic vinegar, give it a good stir then keep the lid ajar so the liquid will evaporate. When removing from crockpot, use tongs and discard any remaining liquid.
