Leftover Prime Rib Sandwich

5 from 48 votes

Leftover Prime Rib Sandwich

If you have leftover prime rib roast, this is a delicious way to make use of the prime rib leftovers. My Prime Rib sandwich is loaded with slices of tender, juicy, medium-rare seasoned prime rib and topped with warm caramelized onions and mushrooms. Finished with a slathering of horseradish sauce.

Prep Time10

Cook Time10

Total Time20

Course: sandwich

Cuisine: American

Servings:

Calories: 533kcal

Ingredients

1 lb leftover prime rib thinnly sliced
1 large sweet onion sliced
8 oz mushrooms sliced
1 cup arugula
1 baguette or hoagie rolls
1 cup au jus
½ cup creamy horseradish sauce *see recipe

US Customary - Metric

Instructions

Prepare your horseradish sauce by mixing the sauce ingredients together in a small bowl and refrigerate until needed.
Melt 2 tablespoons of butter in a large skillet.
When the butter is melted, add the sliced onions and mushrooms to the pan.
Saute the onions and mushrooms over high heat until they begin to brown. Let them cook for 3-5 minutes without moving them around, so they have a chance to begin the caramelization process.
Turn the mushrooms and onions over and reduce to medium heat and let them continue to cook for another 5-7 minutes. Stir them around during this part of the process..
While the mushrooms and onions are cooking, trim the leftover prime rib. Remove the bone and extra fat from the edges of the meat. Take out any fat deposits from the middle of the beef ( I took this picture before removing the piece of fat in the middle)
Sliced the baguette in half log ways so you make a top and bottom.
Slather a good amount of creamy horseradish sauce on the bottom side of french bread.
Add a good handful of arugula (the peppery flavor of arugula improves the overall flavor of the sandwich.
Place thinly sliced prime rib on top of the arugula ( I like to fold the meat, setting it side by side so it’s not just lying on top of each other).
Add the caramelized onions and mushrooms to the sandwich.
*Add a few slices of provolone cheese (or swiss cheese) to the sandwich for additional flavor. If you want melted cheese, add the slices before the warm mushrooms and onions, and the heat will help melt the cheese
Cover with the top of the baguette and cut into sandwiches. Serve with hot au jus and extra horseradish sauce.

Notes

The sweet caramelized onions and mushrooms help make this the Best Prime Rib Sandwich. But if you’re not a fan of mushrooms? It’s okay to leave them out.

Nutrition