Season steaks with salt and pepper. Place on a medium high grill. While the steak is cooking, heat a sauté pan over medium high heat. Add the olive oil. Add the onions and cook for 2 - 3 minutes. Add the garlic and continue to cook for an additional minute. Add the mushrooms and sauté for 2 - 3 minutes. Add the black pepper, thyme, beef broth and port wine. Cook the mushroom mixture until all of the liquid has evaporated. Stir in the fresh herbs. Adjust the seasoning with salt and pepper. Remove the steak from the grill and top with the steakhouse mushrooms.