The Edinburgh Diner Tenderloin Sandwich is a hearty, pub-style sandwich featuring seared beef tenderloin, caramelized onions, melted cheese, and a tangy horseradish mayo, all piled onto a toasted roll. It’s inspired by the classic British steak sandwich but with a diner twist—crisp, buttery bread and a rich, savory sauce make it a satisfying meal. This recipe works because it’s quick enough for a weeknight dinner yet impressive enough for a casual gathering.
Ingredients
- 1 lb (450 g) beef tenderloin, sliced into 1/4-inch (6 mm) medallions
- 2 tbsp (30 ml) olive oil, divided
- 2 large yellow onions, thinly sliced
- 1 tsp (5 g) granulated sugar
- 1/2 tsp (2.5 g) salt, plus more for seasoning beef
- 1/4 tsp (1 g) black pepper, plus more for seasoning beef
- 4 crusty rolls (e.g., ciabatta or brioche), split
- 4 slices (about 4 oz / 115 g) provolone or Swiss cheese
- 1/2 cup (120 ml) mayonnaise
- 2 tbsp (30 ml) prepared horseradish
- 1 tbsp (15 ml) Dijon mustard
- 1 tbsp (15 g) butter, softened
- Fresh arugula or lettuce leaves (optional)
Instructions
- Prep the beef: Pat the tenderloin medallions dry with paper towels. Season both sides generously with salt and black pepper. Let sit at room temperature for 15 minutes while you prepare the onions.
- Caramelize the onions: Heat 1 tbsp (15 ml) olive oil in a large skillet over medium heat. Add the sliced onions and sugar. Cook, stirring occasionally, for 15–20 minutes until deep golden brown and soft. Season with 1/2 tsp salt and 1/4 tsp pepper. Transfer to a bowl and set aside.
- Make the horseradish mayo: In a small bowl, mix mayonnaise, horseradish, and Dijon mustard until smooth. Set aside.
- Sear the beef: Wipe the skillet clean and heat the remaining 1 tbsp (15 ml) olive oil over high heat. Add the tenderloin medallions in a single layer (work in batches if needed). Sear for 1–2 minutes per side for medium-rare, or until the internal temperature reaches 145°F (63°C) for medium (USDA FSIS safe minimum for whole cuts of beef). Remove from the skillet and let rest for 3 minutes.
- Toast the rolls: Spread the cut sides of the rolls with softened butter. Toast in the same skillet over medium heat until golden and crisp, about 1–2 minutes.
- Assemble the sandwiches: Spread a generous layer of horseradish mayo on the bottom half of each roll. Top with a few slices of beef, then a pile of caramelized onions, and finally a slice of cheese. Place the top halves on.
- Melt the cheese (optional): If you want the cheese melted, place the assembled sandwiches on a baking sheet and broil for 1–2 minutes until the cheese bubbles. Watch closely to avoid burning.
- Serve: Add a handful of arugula or lettuce if desired, close the sandwiches, and serve immediately.
Tips
- Don’t overcook the beef: Tenderloin is lean and cooks fast. Use a meat thermometer to hit 145°F (63°C) for medium; anything beyond will be tough.
- Slice the beef thinly: If you prefer a more fork-tender bite, slice the tenderloin into thin strips against the grain after searing, rather than leaving medallions whole.
- Substitute the cheese: Provolone or Swiss are classic, but sharp cheddar or blue cheese also work well. Blue cheese will add a stronger tang.
- Make ahead: Caramelized onions can be made up to 3 days ahead and refrigerated. Reheat gently before assembling.
Serving Suggestions
Serve the sandwich with crispy french fries, a simple green salad, or pickles on the side. For a full diner experience, add a side of coleslaw or potato chips. A cold beer or a sparkling lemonade pairs nicely.
Variations
- Spicy version: Add a few slices of jalapeño or a drizzle of hot sauce to the mayo.
- Mushroom lover: Sauté 8 oz (225 g) sliced mushrooms with the onions for an earthy addition.
- Low-carb: Serve the beef and onions over a bed of greens instead of bread.
- Breakfast twist: Top with a fried egg for a hearty brunch sandwich.
Storage and Reheating
Refrigerate leftover beef and onions separately in airtight containers for up to 3 days. To reheat, warm the beef gently in a skillet over low heat with a splash of beef broth or water to keep it moist. Reheat the onions in the microwave or on the stovetop. Assemble fresh sandwiches with new rolls. The horseradish mayo keeps for up to 1 week refrigerated.
Frequently Asked Questions
Can I use a different cut of beef? Yes, sirloin or ribeye work well. Sirloin is leaner and may need a little more oil; ribeye is fattier and more forgiving. Adjust cooking time accordingly.
What if I don’t have horseradish? Use 1 tbsp (15 ml) of Dijon mustard and 1 tbsp (15 ml) of white wine vinegar mixed with mayo as a substitute. The flavor will be less pungent but still tangy.
How do I know when the beef is done without a thermometer? Use the finger test: press the meat with your index finger—if it feels like the flesh between your thumb and index finger when relaxed, it’s rare; if it feels like the base of your thumb, it’s medium. But a thermometer is always safer.
Can I grill the beef instead of pan-searing? Absolutely. Preheat your grill to high and cook the medallions for 1–2 minutes per side, then rest.
How do I prevent the bread from getting soggy? Toast the rolls well and spread the mayo on both halves—this creates a barrier. Also, avoid piling on too many juicy onions; drain them slightly if they release excess liquid.
Can I make this sandwich dairy-free? Yes, use a dairy-free cheese alternative and skip the butter on the rolls (use olive oil instead). The horseradish mayo is naturally dairy-free if you use vegan mayo.
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More recipes to cook
Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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