Beef with whites

2 lbs lean beef or 2 lbs veal, cut into cubes (or 1 pound of each) 1 medium onion , sliced 1 clove garlic , minced 1 lb white mushrooms or 1 lb baby bella[...]

4 x Fillets steak, each weighting about 140g     Salt and freshly grnd black pepper 3 Tbsp. Vegetable oil 4 lrg Flat mushrooms 20 gm Unsalted butter 4 Tbsp.[...]