Onion Soup in Crock PotSlow Cooker Onion Soup

This onion soup is made with Sam Adams dark beer.
First cooked in a slow cooker then finished
to cheesy goodness under the oven broiler.
This is by far one of my favorite comfort foods.

Ingredients:
1 large red onion
1 sweet white onion
1 large yellow onion
4 fresh cloves garlic, peeled
2 tablespoons unsalted butter
4 tablespoons cheap balsamic vinegar
2 tablespoons dark brown sugar
4 tablespoons all-purpose flour
1 teaspoon Coleman's dried mustard
12 ounces Sam Adams dark beer
4 cups low sodium beef stock
2 tablespoons chopped fresh thyme
salt to taste
ground black pepper to taste
Gruyere cheese for melting
Toasted bread for serving

Directions:
Peel and slice onions really really thin.
Use a mandoline if you have one, I don't!
Mince garic and place in slow cooker with
sliced onions, brown sugar, dried mustard,
unsalted butter and vinegar to taste.
Cover crock pot and let cook for one hour,
Add into the slow cooker the flour, dark beer,
beef stock, salt and ground black pepper.
Turn the temperature of the slow cooker to low
and let cook sitting on the counter for 8 hours.
Dish out soup portions into oven safe bowls.
Cover each bowl with a piece of toasted bread,
a drizzle of balsamic vinegar and gruyere cheese.
Place the bowls under the broiler until cheese melts.