Heat the oil in a large casserole dish. Fry onions until soft. Place flour, mustard, salt and pepper in a bowl and mix well. Toss the meat and kidneys in flour, add to the saccerole and brown on all sides.
Stir in the remaining flour mix. Add swedes, carrots and beer and mix well.
Cover and simmer for 1 and half hours.
10 minutes before serving, add mushrooms and parsley.