Prime Rib Sandwich

Treat yourself to the best Prime Rib Sandwich! This flavorful sandwich is easy to make with just a few ingredients. It's the best way to use up prime rib leftovers. Made with peppery arugula, homemade creamy horseradish sauce, melty provolone cheese, thinly sliced prime rib, and caramelized onions all piled high on a baguette!

Prep Time10

Cook Time45

Total Time55

Course: Main Course

Cuisine: American

Servings: - 6 servings

Calories: 588kcal

Author: Briana

Equipment

Ingredients

4 tablespoons unsalted butter
1 tablespoon white balsamic vinegar
½ - 1 teaspoon kosher salt, divided
¼ - ½ teaspoon black pepper, divided (to taste)
1 pound leftover prime rib, thinly sliced and fat removed
1 large baguette, sliced in half lengthwise and cut into about 4 sections
4 - 6 slices provolone cheese
2 ounces baby arugula (to taste)
6 tablespoons creamy horseradish sauce (about 3 servings)

Instructions

Start with the caramelized onions. Melt the butter in a large skillet over medium-low heat. Add the sliced onions with a pinch of salt. Cook, stirring occasionally, until they begin to soften and turn golden brown. The process will take about 30 to 40 minutes to get to a deep golden brown color. Don’t rush this step; patience is key to creating perfectly caramelized onions.
Once the onions are a nice golden brown, stir in the balsamic vinegar and black pepper, and season to taste with salt. Cook for an additional 2–3 minutes, then remove from heat and set aside.
Meanwhile, while the onions are caramelizing, prepare the prime rib. If the prime rib is cold, gently reheat it in a pan over low heat, or wrap it in foil and warm it in a preheated oven at 300°F for about 10 minutes.
Slice the baguette lengthwise, and then cut it into the desired number of sandwiches. We made three large sandwiches (or 6 small - medium sized ones). Place the baguette slices on a baking sheet.
Spread creamy horseradish sauce on both halves of the baguette. Lay the thinly sliced prime rib over the sauce. Season with a bit of salt and pepper, if desired. Top the meat with caramelized onions.
Add slices of provolone cheese on top of the onions. (About 1.5 slices per sandwich). Place the sandwich (open-faced) under the broiler for 2-3 minutes or until the cheese is melted and bubbly. Watch carefully to avoid burning.
Remove the sandwich from the oven and top with baby arugula, and season the arugula with kosher salt and pepper to taste. Add more horseradish sauce if desired. Now, just assemble the sandwich, and enjoy!
Store leftover sandwiches in an airtight container in the fridge for up to two days.

Notes

Take your time when caramelizing the onions. There’s no rushing it! Be patient when caramelizing onions; they add a rich, sweet flavor to the sandwich.
Slice the prime rib very thin. Use a very sharp knife to get thin, even slices of prime rib. Remove the excess fat. Pull or cut off any pieces of extra fat on the prime rib. It won’t taste great to bite into a large chunk of fat on a sandwich!
Carefully reheat the prime rib. You don’t want to overcook the meat, so heat it very gently. Also, keep in mind that it will heat up a little bit more under the broiler.
Add horseradish sauce to taste. Adjust the amount of horseradish sauce to suit your preferences.
Season the arugula. This will ensure that every bite tastes great.
Watch the sandwich under the broiler closely to avoid burning while achieving that perfect, melty cheese texture.
To reheat. To warm up prime rib for sandwiches, you've got a few options. First off, we don't recommend heating the arugula on the sandwich, so keep this off the sandwich if you can.
- Use a non-stick pan on the stove with a bit of olive oil, turning the slices until they're warmed up.
- Use the oven or air fryer. Another way is to wrap the slices in foil and stick them in a 300°F oven for 10 minutes, or air fryer for about 5 minutes.
- If you're in a hurry, you can even use the microwave. Set the microwave to 50% power, and just be sure to heat the slices in short bursts to avoid overdoing it.

Nutrition