Place brisket in the crockpot with the onions. Mix chiles, beer, tomato paste, cinnamon, pepper, salt, brown sugar and garlic. Pour over the brisket.
Cover and cook on low for 10 to 12 hours.
Cool to room temperature and refrigerate overnight.
The next morning, skim fat from liquid and trim as much fat from the brisket as possible. Add the potatoes and carrots.
Cover and cook on low for 8 to 10 hours.
Servings: 12