For the steak: Heat a large cast-iron skillet over high heat. Sprinkle the steaks on both sides with the seasoned salt and a few grinds of pepper. Brush all over with the melted butter. Add to the pan and sear until a crust forms on the underside, about 4 minutes. Flip and cook until crusty on the second side, 4 to 5 minutes more for medium rare. Let rest 15 minutes. Meanwhile, for the mashed potatoes: Put the potatoes in a large pot, cover with water and season with salt. Bring to a simmer and cook until tender, 10 to 12 minutes. Drain well. While still hot, return to the pot and add the butter, cream cheese, half-and-half, 1 teaspoon salt and a few grinds of pepper. Mash, adding more half-and-half as needed. Once the steaks have rested, slice them against the grain. For the salad: Combine the spinach and mushrooms in a large bowl. Drizzle with the olive oil and vinegar and sprinkle with the salt and a few grinds of pepper. Toss well. To serve, divide the mashed potatoes among bowls. Top with the sliced steak. Mound the salad on top and sprinkle with the blue cheese and fried onions.