Preheat oven to 180º

Melt butter and oil in a pot, brown chicken on all sides. Take chicken out of pan to one side.

Put diced onion into the pot and fry in the butter and oil for 2-3 minutes.

Stir in Orange juice, water, stock cube and tarragon. Bring to a boil and re add the chicken.

Cover with lid or foil and bake for 1 1/2 hours.

Remove chicken onto a plate. Mix cornflour with 2 tbsp water and add to sauce. Return to boil for 2-3 minutes with constant stirring.

Cool sauce slightly and stir in sour cream.

Serve with rice