Place chicken in the bottom of the slow cooker.In a medium bowl whisk together soy sauce, water, brown sugar, sesame oil, rice wine vinegar, hoisin sauce, ginger, garlic and Sriracha.
Pour the sauce mixture ontop of the chicken and cook for 2-3 hours on low.
Remove the chicken from the liquid and place on a plate or cutting board. Allow the chicken to rest for a couple of minutes and then shred with two forks or slice it up with a knife.
Transfer the liquid from the slow cooker to a small saucepan.Whisk 2 tablespoons of water with 1 tablespoon of cornstarch. Slowly add the cornstarch mixture to the sauce. Cook on high until bubbly and thickened, whisking constantly.
Pour the sauce back into the slow cooker along with the shredded chicken and broccoli, toss to coat. Cook for an additional 30 minutes or until the broccoli is tender.
Serve immediately with sesame seeds for garnish, if desired.