Heat oil and butter in a frying pan, add the chicken and fry over until browned. Drain and add to slow cooker.

Add the shallots to the frying pan and cook, stirring for 5 mins. Stir in the flour, then gradually mix in the stock. Add the tarragon, salt and pepper and bring to the boil.

Pour sauce over the chicken, cover with lid and cook on high for 4 hours.

Stir in the cream and tarragon. Serve.