For au jus: In a large skillet, melt butter and stir in olive oil over medium-high heat. Add sliced onion and sweat for 5 to 8 min. or until tender and translucent, stirring occasionally. Stir in Black Dip, broth, thyme, and Salt & Pepper Tableside. Bring to a boil and reduce to simmer. Let cook uncovered for 30 min., and covered for a final 10 min. of simmering. Pour the au jus through a colander to separate the onions from the liquid. Set both aside and keep warm.
For sandwich: While au jus is cooking, bring steaks out of the refrigerator and let come to room temperature and begin heating the grill. Season steaks generously on both sides with Mt. Hood. Grill to medium rare, about 4 to 6 min. per side. Move steaks to a plate, cover, and rest while you toast baguettes in a 350-degree oven for about 5 min. or until just beginning to crisp. Place cheese on each top half of sandwich baguettes and place back in oven to let melt, about 5 more min. Slice steak across the grain into thin strips. Dip steak slices into warm au jus and lay over bottom halves of toasted bread. Top with reserved onions and other baguette halves. Serve with a small bowl of Black Dip au jus on the side for dipping.