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What do you do with leftover prime rib? Make an out-of-this-world Prime Rib Steak Sandwich, filled with tender meat, melted cheese, and sweet caramelized onions, that’s what.
This is pretty much the greatest sandwich there ever was!
It’s possible you’re here because you saw our recipe for Smoked Prime Rib. If not feel free to check it out. It also comes with a video.
Or you may be here because you cooked a prime rib over the holidays and now find yourself with an influx of leftover prime rib. #meatloverproblems
Or you’re just having mad cravings for an overindulgent meaty, cheesy, creamy, prime rib steak sandwich layered with the sweet goodness of caramelized onions.
Whatever the reason, we have the answer. It lies within the sweet, smoky, meaty, goodness of this sandwich.
This is the BEST use for leftover Prime Rib (smoked or otherwise).
Or any leftover steak really. And it’s as simple as warming up your meat, cooking some onions, and assembling.
How Do You Warm Up a Precooked Prime Rib?
Depending on how much steak you have, there are several options for warming up your meat. If you have about 2 lbs, like you see in the photo then you can take your roast and place it in the oven, set to 325, for about 15 minutes or until warmed throughout. You can use an instant read thermometer to avoid overcooking the meat. You don’t want to start cooking it again, you just want to warm it up. The length of time it will require to re-heat will depend on how much meat you have.
You can also just slice the cold meat and heat it up on the stove-top. You can also serve the meat cold. I won’t judge. But really, this prime rib steak sandwich is best made warm, with the ooey goodness of melted cheese smothering the warmed meat.
How to Caramelize Onions
While the meat is warming you can caramelize your onions. Just slice one onion and cook it on the stove-top until slowly caramelized and sweet. This takes time for perfect caramelization. Roughly 30-40 minutes if you’re doing it right. But believe me, it’s worth every single minute for the sweet glory of perfectly caramelized onions.
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While all this is going on you can prep your creamy horseradish sauce. If you’re a traditionalist then it’s possible you used horseradish when you made your prime rib? Therefore it’s possible you have some leftover? If so you can just use that to make this creamy sauce. Or if you frequently make Bloody Mary’s at home then it’s likely you already have some in your fridge. And for all you mayo-haters out there (I’m raising my hand high), this sauce is mayo-free. I want something creamy, but not too rich or oily. So I like sour cream as the base, then add in horseradish, chives and a few other ingredients for flavor.
Next all we need to do is assemble the steak sandwich.
How to Make the Best Leftover Prime Rib Steak Sandwich
To start I like a baguette for ease and crunch and for serving a group. And if you’re serving 4 or 5 people, it’s the perfect size.
- Portion the baguette into about 5-inch segments, and slice open lengthwise.
- Place a couple slices of provolone cheese on the bottom piece and place the bread and cheese under the broiler to melt.
- Once the cheese is melted (around 2 minutes), you can layer on your meat, arugula (or other crunchy greens), caramelized onions, and top with a generous drizzle of the horseradish cream sauce.
And you’ve got a winning leftover prime rib sandwich. Who knows, you may start smoking a prime rib just so you can use the tender slices to make these sandwiches? Just sayin.
Prime Rib Recipes
- Smoked Prime Rib with Herb Crust
- Smoked Prime Rib with Horseradish Butter
- Wine Pairing for Holiday Prime Rib
- Prime Rib French Dip Sandwiches
Prime Rib Sandwich Recipe
Prime Rib Steak Sandwiches
Ingredients
- 1 ½ lbs leftover prime rib, or other steak (about 4-6 oz per person)
- 1 white onion, sliced
- 8 slices provolone cheese
- 2 cups arugula, or other crunchy green, lightly packed
- 1 large baguette
For the Horseradish Cream Sauce
- ¾ cup sour cream
- 3 tablespoons horseradish
- 1 tablespoon Dijon mustard
- 2 tablespoons fresh squeezed lemon juice
- 1 tablespoon white wine vinegar
- ½ teaspoon kosher salt
- 2 tablespoon fresh chives, finely chopped
Instructions
For the Prime Rib Sandwiches:
- Preheat oven to 325 degrees.
- To make the caramelized onions: heat up a large pan on the stovetop to medium heat then add 2 tablespoons olive oil and the sliced onions. Stir occasionally until the onions are soft, golden/starting to brown, and sweet to the taste (roughly 30-40 minutes). Remove from heat. *You may need to adjust the heat and turn it down if they are browning too fast.
- In the meantime, place your leftover prime rib in a large cast iron (or oven proof) pan and place in the oven to heat up (approx 15 – 20 minutes). Remove from oven and slice into thin slices.
- To build your sandwiches: cut the baguette into 4 equal size pieces and cut in half, lengthwise. Place on a baking sheet, open faced, and place two pieces of cheese on bottom half of each sandwich.
- Place under the broiler for a couple minutes to melt the cheese (paying close attention to not burn the bread).
- Once the cheese is melted, remove from the oven and build each sandwich: add 3-4 slices of the warm steak, a small handful of arugula, and a couple tablespoons of caramelized onions, then top with 1-2 tablespoons of creamy horseradish sauce. Serve immediately and enjoy the heck out of these epic sandwiches.
For the Horseradish Cream Sauce
- Place all ingredients in a bowl and mix together.
Notes
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
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Perfect in every way. I warmed my already thinly sliced prime rib in the same skillet as the onions (less clean-up). Bravo!! Thank you.
My wife says this is the best sandwich she has ever had and I agree. The caramelized onions were fantastic.
The only thing I did different was put my leftover prime rib in a bag and sous vide it for 1 hour at 140 degrees.
I made this as written, on sourdough. It was wonderful.
My men loved this sandwich! It is the bomb! The horseradish cream was the best addition!
Absolutely amazing! We thinly sliced our prime rib, put in the oven for about 15 minutes. My husband made his with Au jus. He doesn’t like cheese or the horseradish sauce. He’s missing out!
All I can say is Dayum! Awesome sandwich. We had a leftover slab of smoked prime rib and I was tired of just making French dips with those kind of leftover cuts. This was a great way to offset the smoke and brighten up the sandwich. Very, very good prepared as directed. This might be a great one to experiment with some pickled onion too.
Amazing… Used leftover prime rib and served as sandwiches today for Father’s day… At bit hit.
Awesome Anita, thanks for sharing!!!
Gorgeous photos!! The carmelized onion, arugula, and roast sounds like an amazing combo!
Ooohhh – These look and sound SO good! I made a prime rib last weekend too, and unfortunately for us, I just missed your recipe. Fortunately for our dog, she scored some awesome leftover prime rib! That horseradish sauce sounds AMAZING!
What a lucky dog!! We’ve been using up our leftovers in tons of delicious ways since making our prime rib. And unfortunately for our dogs, they haven’t received any of it 😉
I love your tip on how to reheat the prime rib – I’m always torn on how to reheat meats because I like it medium rare and so with my leftovers the next day if I have it cold it stays that way but I know I like it warm better to get more juice enjoyment
Thanks! This is key for a meat like prime rib that is best served rare (to med rare) and tender. Reheating it at too high of a temp and for too long you run the risk of overcooking it.