Season the chicken thighs with salt and pepper, rubbing it into all sides.
Heat a large skillet over medium-high heat, and once hot add olive oil.
Add the chicken and brown on both sides, about 3-4 minutes each side.
Transfer the chicken to the crockpot, and add carrots, potatoes and onions.
In a small bowl, whisk together brown sugar, garlic, soy sauce and ketchup.
Pour the sauce mixture on top.
Cover the lid and cook for 2-4 hours on High or 4-6 hours on Low.
(Optional) Broil the chicken for 2-3 minutes before serving for additional crispiness and color.
Remove the chicken and veggies onto serving plates.
(Optional) Thicken the sauce by adding a slurry of 1 tablespoon of cornstarch mixed with 1 tablespoon water. Cook for about 10 minutes until the sauce is thickened.
Drizzle with sauce and garnish with optional parsley.