Place Frozen Chicken Breasts, spice pack and cooking sauce (from Stubb’s Cookin’ Sauce package) and quartered onions into slow cooker. Cover and cook on low for 6-8 hours or high for 4-5 hours. After cooking, drain liquid from slow cooker and shred chicken with forks. Pour finishing sauce (from Stubb’s Cookin’ Sauce package) over meat and heat on low for 30 minutes.
Serve over buns with your favorite extras like slaw, pickles or bacon.