Prepare the Base: Place the diced onions, minced garlic, sliced carrots, and mushrooms into the bottom of a 6-quart slow cooker.
Season the Chicken: Toss the chicken chunks with salt, pepper, and smoked paprika. If you are searing the meat, do it now in a skillet for 2 minutes per side, then transfer to the slow cooker.
Combine: Place the chicken on top of the vegetables. Sprinkle the dried thyme and rosemary over the top.
Liquid Gold: Pour the chicken broth over everything. Add the butter on top in small pats.
Slow Cook: Cover and cook on LOW for 5-6 hours or on HIGH for 3-4 hours. You want the chicken to be tender enough to break with a spoon.
Thicken the Sauce: About 30 minutes before serving, whisk your cornstarch and water together to create a slurry. Stir this into the bubbling stew. Turn the slow cooker to HIGH (if it wasn’t already) and let it thicken for the remaining 30 minutes.
Final Touch: Taste and add more salt or pepper if needed. Stir in a generous handful of chopped fresh parsley.