Peel the apples, garlic and shallots.
Cut the celery into pieces and cube the apple.
Put a tablespoon of the oil in a frying pan over a medium heat and add the shallots, apples, celery and lardons.
Cook for 5 minutes, stirring occasionally until the bacon is pink and the onions lightly coloured.
Add the garlic and tarragon and cook for a minute.
Transfer the vegetables to the slow cooker with a slotted spoon.
Add the remaining oil to the pan over a medium to high heat.
Season the meat and sear all over in batches.
When all of the meat has been seared, return it to the pan.
Sprinkle over the flour and cook for a minute, stirring.
Gradually add the cider and stir in the mustard.
Bring to a simmer, stirring all the time. The sauce will thicken.
Pour the mixture over the vegetables in the slow cooker.
Cook on HIGH for 4 - 5 hours, or LOW for 7 - 10 hours.
Check the seasoning and stir through the crème fraîche 30 minutes before serving