Heat 2 tablespoons of oil in a flameproof lidded casserole and brown the beef for 5 minutes.
Remove the meat and fry the onions and garlic in the remaining oil for 5 minutes.
Stir in the beef stock and scrape any browned bits from the bottom of the pan.
Whisk the flour with the wine in a bowl to form a smooth batter.
Return the meat to the pan and pour in the wine mixture.
Boil until thickened, add Worcestershire sauce and sugar, then season with salt and pepper.
Cover and simmer gently for 2 hours.
Add the mushrooms, return to boiling, then cover and simmer for another 30 minutes.
Mix mustard, horseradish, and optional cream in a bowl.
Stir the condiment mixture into the casserole and serve.