In a saucepan over medium-high heat, add chicken and chicken broth. Cook for 20 minutes. Remove chicken from pan to a bowl and shred.
In a smaller saucepan over medium-low heat, add sauce ingredients, stir to combine. Let simmer on low while chicken is cooking. Once chicken is shredded pour sauce over and toss to coat.
Preheat griddle to medium. Combine oil, garlic powder and parsley. Brush over one side of each piece of bread. Build sandwiches with brushed side of bread on the outside. Start with bread, then layer with slice of provolone, a few slices of onion, a portion of BBQ chicken, slice of cheddar and top bread piece. Place each sandwich on the griddle and cook for 5 minutes on each side.