To the slow cooker add onion, garlic, chicken thighs, mushrooms, celery, Dijon mustard, celery salt, bay leaves, and tomato paste. Pour in the chicken stock, white wine, and Worcestershire sauce. Gently combine all ingredients. Cover with the lid and set the cooker on low for 8 hours or high for 4 hours.
1 onion, 4 cloves garlic, 600 g chicken thighs, 250 g button mushrooms, 2 celery, 1 tbsp dijon mustard, 1 tbsp celery salt, 4 bay leaves, 1 tbsp tomato paste, 125 ml chicken stock, 100 ml white wine, 2 tbsp worcestershire sauce