Fry your bacon lardons either in a small frying pan, or in the bottom of your slow cooker pan if it can be used on the hob. Let them go crispy and golden brown.
Meanwhile, put your chicken thighs in a large bowl and coat thoroughly in the flour.
When the bacon has finished cooking, put the onions, celery, carrots and bacon pieces into your slow cooker (or leave the bacon pieces in that pan if they've been cooking in there).
Sit the flour rolled chicken pieces on top of the vegetables in the slow cooker.
Mix the stock, mustard, thyme and salt and pepper and pour into the slow cooker, around the side of the chicken.
Put the lid on and cook on HIGH for 4 hours or LOW for at least 6 hours.
When you're ready to serve, add the creme fraiche and the chopped parsley. Check for seasoning and add more salt and pepper if needed.