Heat slow cooker on low setting. To slow cooker, add garlic, shallot, leek, celery, mushrooms, onions, 2 tbsp butter, 1 cup chicken stock, sea salt and black pepper. Cover, and cook vegetables on low for 1 hour. Complete this next step while the vegetables are cooking – In a large skillet over medium-high heat, pan-sear the chicken breasts in the remaining 2 tbsp butter until they are browned on both sides. – About 5 minutes each side. (Chicken will not be fully cooked during this stage.)
