Season the steaks well with salt and freshly ground black pepper.

Heat a frying pan until smoking, add the butter and olive oil and fry the steaks on both sides for 2-3 minutes (for medium), or until cooked to your liking.

For the sauce, heat a clean frying pan until smoking, add 25g of the butter and fry the shallots for 2-3 minutes, or until golden-brown. Add the mushrooms and garlic and cook for one minute, then pour in the wine and simmer for 3 minutes.

Add the chicken stock and simmer for 10 minutes, or until the liquid has reduced by half. Whisk in the remaining butter until the sauce is smooth and creamy. Stir in the tarragon leaves and season, to taste, with salt and freshly ground black pepper.

Plate up the steaks and spoon the sauce over the top.