A juicy steak sandwich with sweet onions and a side of onion rings.
Double Onion Dip
Preheat oven to 400. To prepare the beef tenderloin, smear on mustards and crust well with sea salt and pepper on all sides.
Heat olive oil in a cast iron or heavy, oven safe pan over high heat. When oil begins to smoke, sear all sides until crust is dark golden.
Place pan in oven to finish cooking; about 10 minutes for medium rare. Remove from heat and let rest at least 15 minutes.
To prepare onions, heat 2 tbsp butter and 2 tbsp olive oil in medium pan over medium heat. Saute onions until softened and lightly coloured, about 5-7 minutes. Season to taste with salt and pepper.
To prepare mushrooms, heat remaining 2 tbsp butter and olive oil in large pan over high heat. Saute mushrooms and thyme until well coloured, about 8-10 minutes. Season to taste with salt and pepper
To assemble, mix Dijon and grainy mustard together. Carve steak into thin slices, reserving any juices.
To assemble sandwich, split baguette into 4 portions. Lightly toast and spread thinly with mustard mix.
Fill each sandwich with steak, sautéed onions and mushrooms. Finish filling with arugula and spoon over any steak juices. Serve with onion rings.
Combine all ingredients for buttermilk marinade: buttermilk, garlic powder, thyme, marjoram, salt and pepper. Soak onion slices for at least one hour, overnight is best.
Preheat oven to 250. Drain onions, reserving marinade. Place 2 cups of flour in a medium mixing bowl; slowly whisk in enough reserved marinade (about 2 cups) to form a loose paste the consistency of pancake batter.
Fill a small deep pot about 1 ½ to 2 inch deep with vegetable oil, making sure level of oil does not reach more than halfway up the pot. Bring oil up to 340-350
Lightly flour onion rings in remaining ¼ cup flour. Dip into batter and drop, one or two at a time, into hot oil. Fry until deep golden brown and remove to drain on a paper towel-lined plate.
Season onion rings with salt while they are still warm. Keep onion rings warm in a low oven.
Preheat oven to 350. Place onion in a piece of aluminum foil; drizzle over olive oil, wrap in a loose package and bake until tender and golden, about 15-20 minutes.
Unwrap and when cool enough to handle, chop into a rough mash. Combine sour cream, mayonnaise and hot sauce in a medium bowl.
Add chopped onion and green onions. Fold to combine and season to taste with salt. Cover with plastic wrap and keep refrigerated until serving.