As amazing as the roast beef dinner is, I think that my favourite part has to be using the leftovers to make roast beef sandwiches! The basic roast beef sandwich is so easy to make and yet so good! I like to start my roast beef sandwiches off with some sweet caramelized onions, which take a bit of time to make but for what they add to the sandwich, they are so worth it! Next up I like to add a bit of bite and I am always torn between using some horseradish or some grainy mustard so I very often just decide to combine the two along with some creamy mayonnaise. Cheese is always a welcome addition to any roast beef sandwich and you can go with some sharp and tangy cheddar or some smooth and creamy swiss or provolone and since melted cheese is always better, you can throw your sandwich under the broiler for a minute or two. No roast beef sandwich would be complete without a hit of tasty gravy, also leftover from the roast beef dinner, and I often like to add something green in the form of peppery arugula. No matter how you do it, you really cannot go wrong with a roast beef sandwich!
Roast Beef Sandwich with Caramelized Onions and Grainy Mustard, Horseradish Mayo
The best part of the roast beef dinner might just be in using the leftovers to make roast beef sandwiches! Tender roast beef with sweet caramelized onions and the bite of a touch of horseradish.
ingredients
- 1 tablespoon olive oil
- 4 cups onion, sliced
- 1/2 cup water
- 4 buns, cut in half and lightly toasted
- 4 slices cheese, cheddar, swiss or provolone
- 1 pound roast beef, warm and thinly sliced
- 1/4 cup gravy
- 2 tablespoons mayonnaise
- 1 tablespoon horseradish
- 1 tablespoon grainy mustard
- 1 handful arugula (optional)
directions
- Heat the oil in a pan over medium heat.
- Add the onions and water and cook, covered, until completely tender and caramelized and golden, about 40-50 minutes, adding more water as needed.
- Mix the mayo, horseradish and mustard.
- Assemble sandwiches and enjoy!
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Rosa's Yummy Yums says
November 29, 2011 at 12:06 pmWow, droolworthy! That is a terrific combination. I am in awe in front of your pictures.
Cheers,
Rosa
bellini says
November 29, 2011 at 1:45 pmThis really is a killer roast beef sandwich Kevin!
nashnordin says
November 29, 2011 at 2:30 pmMy! This looks fabulous! I love caramelized onions!
Sara Jahan says
November 29, 2011 at 2:51 pmMy mouth is literally watering. So going to try this recipe!!
Xoxo,
Sara
Dining Alone says
November 29, 2011 at 4:42 pmOh wow this looks so good, my husband would even eat this!
Delishhh says
November 29, 2011 at 7:50 pmOh YUM that looks so good right now for lunch!
anniebakes says
November 29, 2011 at 9:57 pmyou always make my mouth water!!
Twin Tables says
November 29, 2011 at 10:04 pmWe couldn't agree more. We love both roast beef and leftover sandwiches…horseradish is a definite must! Love your sammy!
Andrea says
November 30, 2011 at 1:00 amLooks very good. I too love a good sandwich.
Chris says
December 7, 2011 at 8:13 pmI agree, the leftovers are the best part.
Jennifer Swedlund says
December 3, 2012 at 4:38 pmWhat cut of meat did you use, and do you mind sharing your recipe for the original roast dinner?
Kevin says
December 8, 2012 at 4:50 pmJennifer Swedlund: I used a sirloin tip but any tender cut such as a top sirloin, strip loin, etc would also work. Here was the roast beef recipe: https://www.closetcooking.com/2011/11/perfect-roast-beef.html
Anonymous says
December 23, 2013 at 4:15 pmJust made this, it was absolutely corking. The horseradish + mustard mayo with the onions was an amazing combination
Patrick says
November 23, 2016 at 11:17 pmI'm definitely making this with leftovers. Just one question on the "1/4 cup of gravy"–does it get mixed into the mayo, mustard, horseradish dressing? Or is it just another level of flavor to put on the sandwich? Or is it meant to heat up the meat in the gravy? I might just experiment!
kevin says
November 24, 2016 at 2:31 pmPatrick: I usually just place a dollop on top of the meat in the sandwich but you could also toss it with the meat when you warm it! Enjoy!