Peel and chop the onions. Wash the thyme and remove the leaves from the stems. Clean and wash the porcini mushrooms. Depending on the size, cut in half or a little smaller. Wash steaks and dab dry.
Heat the oil. Brown the steaks well on each side. Season with salt and pepper. Add onions and mushrooms to the frying fat. Fry over medium heat for about 5 minutes, turning over. Season with salt, pepper and thyme.
Cut the baguette into thin slices. Briefly toast and serve.