Ingredients
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1/2 cup mayonnaise
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1/4 cup white horseradish, prepared
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4 tablespoons butter (1/2 stick, divided)
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3 beef tenderloin steaks, thick
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8 ounces shiitake mushrooms, stemmed, caps thinly sliced (about 5 cups)
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1 cup beef broth
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4 large croissants, halved horizontally, lightly toasted
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2 cups arugula
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3 medium onions, thinly sliced
Instructions
- Mix mayonnaise and horseradish in small bowl to blend.
- Melt 1 tablespoon butter in heavy large skillet over medium-high heat. Sprinkle tenderloin steaks with salt and pepper. Add steaks to skillet and cook to desired doneness, about 5 minutes per side for medium-rare. Using tongs, transfer steaks to work surface.
- Melt 3 tablespoons butter in same skillet over medium-high heat. Add onions; sauté until dark brown, about 25 minutes. Add mushrooms; sauté until tender, about 5 minutes. Add broth; boil until juices are reduced to glaze, stirring occasionally, about 1 minute. Season onion mixture to taste with salt and pepper.
- Place 1 croissant bottom, cut side up, on each of 4 plates. Spread each with horseradish mayonnaise and top with 1/2 cup arugula. Thinly slice steaks and divide among croissants. Top with onion mixture. Spread remaining mayonnaise on cut side of croissant tops. Place tops on sandwiches.