Begin by patting the chicken dry with a paper towel to ensure it sears well. Season generously with salt and black pepper, then set the chicken aside on a plate.

In a skillet, heat 1 tablespoon of olive oil over medium-high heat. Once shimmering, add the chicken and sear for 2-3 minutes on each side until golden brown.

In a medium bowl, whisk together honey, Dijon mustard, yellow mustard, soy sauce, apple cider vinegar, and minced garlic until smooth.

In your slow cooker, layer the sliced onion on the bottom. Place the seared or raw chicken pieces on top, then pour the prepared sauce evenly over them.

Cover the slow cooker and set it to low for 6-8 hours or high for 3-4 hours. Cook until the chicken reaches an internal temperature of 165°F and is tender.

Once cooked, carefully remove the chicken and shred it using two forks if using thighs; if using breasts, keep them whole.

If you prefer a thicker sauce, mix cornstarch with cold water to create a slurry. Stir this into the slow cooker, set it on high, and cook for an additional 10-15 minutes.

Garnish with fresh parsley or green onions and serve alongside rice, quinoa, or your favorite steamed vegetables.