Trim roast of any excess fat and place in a slow-cooker and top with pepperoncinis and onion.

In a separate bowl combine the remaining ingredients and whisk until smooth.

Measure 1½ C of the sauce and set aside. Pour remaining sauce over the meat, cover and let cook on low for 6-8 hours or high for 4. Meat is done when tender and shreds easily.

Transfer reserved sauce into a sauce pan and bring to a simmer. Reduce for 15- 20 minutes over medium heat until it has thickened and coats the back of a spoon. Remove from heat.

When meat is done, remove from slow-cooker and shred into bite-sized pieces. Discard the cooking liquid and return meat to the slow-cooker.

Stir thickened BBQ sauce into the shredded meat and heat until hot throughout. Serve on soft rolls topped with onion rings and pepperoncinis if desired.