SEASONING: In a bowl, combine the cornstarch, dried parsley, chicken bouillon, onion powder, garlic powder, dried dill, and white pepper.
SEASON: Sprinkle the seasoning over the chicken breasts evenly on both sides.
OPTIONAL: Heat a large non-stick or cast iron skillet over medium heat. Melt 1 tablespoon of butter in the skillet. Place the chicken in the skillet and allow it to sear for 1-2 minutes on each side.
FILL: Pour the soy sauce, Worcestershire, buttermilk, and the reserved pickling liquid in the bowl of a slow cooker and whisk to combine. Place the chicken breasts on top. Sprinkle with the sliced onions, speckle with cubes of butter over the chicken, then add the pepperoncini peppers on top.
SLOW COOK: Cover the slow cooker with the lid and cook on high for 2½-4 hours, or low for 4-7 hours. I cook chicken breasts on low and find that they are typically done closer to 4 hours, thighs will take closer to 7. Ultimately, it depends on the size of the chicken thighs/breasts.
SHRED: When the chicken is done, shred using two forks or in this chicken shredder and serve with prepared mashed potatoes, no knead bread, on focaccia bread or in tacos, or with a house salad.