In a large bowl whisk together the BBQ sauce and honey.
Melt your butter in a cast iron skillet or a heavy bottomed dutch oven over medium heat. Working in batches brown the chicken, just about a minute on each side.
Spray the slow cooker with cooking spray. Pour some of the sauce in the bottom of the crock pot. Put the chicken in the crock pot and cover them with the remaining sauce. It's okay if some of the chicken is layered.
Cook on low for four hours or until a meat thermometer registers 165 degrees.
Remove the chicken from the crock pot and plate on the serving platter. Add the cornstarch to the sauce, whisking it to combine. With the crock pot still on low, cook for five minutes. Pour some of the sauce over the chicken.