If you use frozen meat - defrost until it softens. Then slice it to thin pieces.
Peel the onion and dice very finely.
Put the butter and olive oil in a pan and fry the onion slices until golden brown. Turn up the heat and place the meat into the pan. Fry a little brown on meat. Lightly flour the meat and season with pepper.
Add the meat broth and simmer gently under the lid for half an hour. If using mushrooms, add them at the end of the cooking process.
Garnish with fresh thyme and serve with lingonberry jam and creamy potatoes or rice.