Melt the 50g of unsalted butter in a non stick frying pan, until foaming. Add the apple and gently sauté 2-3 minutes.
Stir in the partridge and cook gently to colour slightly. Be careful not to overcook – the meat should be rose pink inside.
Remove the apple and partridge and keep warm.
Add the cider and ¼ stock cube to the pan. Bring to the boil, then simmer to reduce by half.
Add the tarragon, sugar, and salt and pepper to taste. Then add the remaining 25g of butter and swirl through.
Tip the partridge and apple back in the pan and stir to coat in the sauce. Serve.