In a heavy pan, heat oil and butter until butter is melted and bubbling but not brown. Add onions and garlic and cook until soft and transparent. Add steak and cook through, breaking up into fine pieces for about 5 minutes - until juices separate.
Add flour, stock powder, tomatoes and finally beer gradually - stirring all the time. Next add frozen veggies, oregano and parsley, salt and pepper to taste. Cook for about 14 minutes then cool slightly and transfer into ramekins or a casserole / pie dish.
Meanwhile peel and steam potatoes for approx 30- 40 mins until soft. Mash finely and mix with cheese and a little milk or cream if you would like. (Very good for the waistline!!)
Spread potato on top of meat mixture and dot with butter and a little more cheese if you like. Cook in a pre-heated oven (180 degrees C) until golden on the top and warmed through. Serve hot - accompanied with warm crusty bread.