Preheat the oven to 425°F. Toss the potatoes with salt and olive oil, and spread on a baking sheet or metal pan. Roast for 20 to 30 minutes, until lightly browned.
Use the dry method for quickly caramelizing onions by placing the onions, along with a pinch of salt and a dash of oil, in a medium-sized sauté pan over medium-high heat. Caramelize the onions and transfer to a plate when done.
Return the pan to the stove over medium heat and add 2 tablespoons of olive oil. Add the mushrooms, stir to coat with the oil, and cook over medium-high heat for 5 minutes. Add the garlic and cook for another minute.
Bring to a simmer and cook, stirring the mushrooms occasionally, for about 5 minutes. Transfer the onions back to the pan, and continue stirring over medium heat until sauce has reduced and thickened, about 10 to 15 minutes. Remove from heat and set aside.
In a separate heavy-bottomed pan, like a cast iron skillet, heat 2 tablespoons oil over high heat. Season the steaks on both sides with salt and pepper, then add to the skillet. Cook for 4 1/2 minutes, flip, and cook for another 4 1/2 minutes on the other side. This will cook the steaks to medium-rare; cook a minute or two longer on each side if you like your steaks more well done. Remove from pan and rest, covered with foil on a cutting board, for 5 minutes.
Check the potatoes. If tops are browned and potatoes are tender, take the tray from the oven and sprinkle blue cheese on top of each one. Place back in oven, on a lower rack, and turn to broil. Continue cooking for an additional 5 minutes. Reheat mushrooms and onions, if necessary, plate them on top of the steak. Remove potatoes from the oven, serve, and enjoy!