For the sauce, heat 1 TBS of vegetable oil in a large saucepan over a moderate to high heat. Add 2 onions, ½ tsp black pepper, 8.8 oz. of button mushrooms, ¼ bunch of thyme and 1 garlic clove, then cook until soft and lightly browned.
Add 1⅔ cups of brandy, ¾ cup of red wine and ¼ bunch of tarragon tied and reduce to a syrup. Add 1 cup of chicken stock and simmer gently to reduce by half. Remove the thyme and tarragon, add drippings from the beef (at least ¼ cup), mix in 7 oz. of crème fraîche.
Taste and adjust the seasoning if necessary.
Add 1⅔ cups of brandy, ¾ cup of red wine and ¼ bunch of tarragon tied and reduce to a syrup. Add 1 cup of chicken stock and simmer gently to reduce by half. Remove the thyme and tarragon, add drippings from the beef (at least ¼ cup), mix in 7 oz. of crème fraîche.
Taste and adjust the seasoning if necessary.