Use garlic press to crush 3 cloves garlic into medium bowl. Stir in soy sauce, pepper, and ½ teaspoon seasoned salt. Place steaks in marinade, turning to coat all sides (wash hands); let stand 10 minutes to marinate.
Crush remaining 2 cloves garlic into microwave-safe bowl. Add onion powder, 1 tablespoon butter, and remaining ¼ teaspoon seasoned salt; microwave on HIGH 1–1 ½ minutes, stirring halfway through cook time, until hot and fragrant. Let stand to cool completely (about 5 minutes).
Meanwhile, coat grill rack with spray and preheat grill (or grill pan) on medium. Cut remaining 3 tablespoons butter into small pieces; add cubed butter, blue cheese, and thyme to melted butter–garlic mixture and stir until well blended. Chill until ready to serve.
Place steaks on grill (discard marinade); grill 6–7 minutes on each side until steaks are 125°F (for medium rare; warm red center), 130°F (for medium; warm pink center), or up to 170°F (for well done). Transfer steaks to cutting board and let rest 5 minutes before slicing; temperature will rise 5–10°F during this time. Cut steaks into portions, top with blue cheese butter, and serve.
Preheat large sauté pan on medium-high 2–3 minutes. Place butter and onions in pan. Crush garlic into pan using garlic press; cook and stir 1–2 minutes until onions and garlic are golden.
Stir in mushrooms, wine, and seasoned salt. Reduce heat to medium and cover; cook and stir 5 minutes or until mushrooms are desired tenderness. Serve.