If desired, spray the inside of your slow cooker with cooking oil. For softer onions, place them at the bottom of the slow cooker, then put the chicken on top of the onions, followed by the jalapenos, garlic and ginger. *If you like more texture to your onions, add them on top of the chicken with everything else.
In a small mixing bowl or liquid measuring cup, combine the brown sugar, soy sauce, Chinese black vinegar, toasted sesame oil, black pepper and white pepper. Give it a stir until the brown sugar has dissolved, then pour it over everything in the slow cooker. Place lid on slow cooker and cook 3-4 hours on low or until the chicken has reached 165℉.
With a slotted spoon or tongs, transfer the chicken from the slow cooker to a plate while we make a cornstarch slurry. Turn the slow cooker to high. Leave the sauce in the slow cooker.
In a small bowl or liquid measuring cup, combine the cornstarch and cold water and stir until fully incorporated. Pour the cornstarch slurry into the slow cooker with the sauce and stir to combine. Add the chicken back to the slow cooker and let thicken for 10-15 minutes with the lid ajar. The sauce isn't going to be "thick", as it is a light sauce, but it will slightly thicken. We love spicy, so we serve the jalapeno and onion from the slow cooker with the chicken. Garnish with toasted sesame seeds and sliced scallions when serving and drizzle the sauce in the slow cooker over the chicken. Enjoy!
Notes
The 4-6 servings are dependent on how many chicken thighs each person has. I get about 10-12 boneless, skinless thighs in 3 pounds, so that averages 5-6 servings when served 2 each or 3-4 servings when served 3 each.
If you can't find Chinese black vinegar, you could try balsamic vinegar. It's not 100% the same, but similar.
Chicken breasts can be used instead of thighs, but I think thighs work really well with this recipe.
Store leftovers in an air-tight container in the fridge and use within 3-4 days. Can also be frozen in freezer-safe containers. For the best quality, use within 3 months.