Mustard steak

Switch on the oven grill. Use the oven roasting tin and place the rack on top.
Blend the vinegar and half the oil in a flat dish. Add the mustard and mix. Place the fillet slices in the dish, turning the meat so the marinade coats it all over.
Cut a cross in each tomato and place on the rack of the oven roasting tin along with the mushrooms.
Brush the vegetables with the remaining oil. Place the fillet slices on the rack. Place the oven roasting tin 100 mm below the oven grill and grill for 3 minutes on one side.
Turn the fillet slices and spoon a little of the mustard marinade on top. Top each slice of meat with a bay leaf.
Place a knob of garlic butter inside each mushroom.
Grill for another 2 to 4 minutes for underdone meat or 4 to 7 minutes for
medium done meat. Season with salt and pepper to taste.
Serve immediately.