Trim any excess fat from pork roast. Prick roast all over with a fork. Rub garlic on roast and rub in the salt and pepper as well. Let sit.
In a small bowl, combine 1 cup brown sugar, mustard and vinegar. Rub all over the roast.
Place the roast in a crockpot with the chicken broth and cook on low for 8-9 hours. Pour off excess juice and set aside to make gravy if desired.
Combine ⅓ cup brown sugar with cinnamon. Spread mixture over top of roast and cook for 1 more hour before serving.
To make gravy: Prior to serving, ladle out about ¼ cup of the juice in the crock pot and strain into a measuring cup. Whisk in 2 tsp cornstarch. Add in enough juice to make 1 cup. Microwave on high for 30 seconds and whisk again. Drizzle sauce over meat prior to serving.
