Grease a slow cooker and lay the chicken it in. Sprinkle the onion over the top.
In a bowl, whisk together the soy sauce, ketchup, garlic, honey, sriracha, ginger and basil. Pour that mixture over the top of the chicken and onions.
Cook on low heat for 5-6 hours OR on high heat for 3-4 hours.
Once it's finished, remove the chicken to a cutting board and shred it. Then mix the cornstarch and water together in a small bowl to form a slurry and stir that in to the remaining sauce in the slow cooker.
Stir the chicken back into the sauce and place the lid back on. Let it cook on high heat for 15 or so more minutes, until the sauce thickens up a bit.
After that you're ready to serve. Store any leftovers in the fridge.
