Prime Rib Sandwich

5 from 2 votes

This prime rib sandwich is the best way to use up leftover prime rib roast! This easy recipe is made from a warm ciabatta roll topped with sweet caramelized onions, horseradish mayo, and seasoned fresh arugula--and it might be your new favorite sandwich.

Prep Time10

Cook Time30

Total Time40

Course: Main Course

Cuisine: American

Keyword: leftover prime rib sandwich, prime rib sandwich

Servings: servings

Author: Elena Davis

Ingredients

For the Caramelized Onions

2 large yellow onions thinly sliced
2 tablespoons butter
salt and pepper to taste
1 pinch sugar optional

For the Horseradish Mayo

1-2 tablespoons horseradish sauce adjust to taste
2-3 tablespoons mayonnaise

For the Arugula

2 cups arugula or baby arugula
1 tablespoon olive oil
1 teaspoon lemon juice

For the Sandwiches

12-15 ounces leftover prime rib thinly sliced
4 ciabatta rolls or 8 slices of baguette bread
butter or olive oil for grilling or toasting the bread
4 slices Swiss cheese or provolone cheese (optional)

For the Au Jus Dip (Optional)

reserved juices from the cooked prime rib
beef broth or beef stock if needed
salt and pepper to taste

US Customary - Metric

Instructions

Caramelize the Onions

In a pan, melt butter over medium-high heat. Add the thinly sliced onions and let them get brown on the bottom before turning. Reduce heat to medium-low and simmer until they become soft and caramelized. This process can take 20-30 minutes. Season with a pinch of sugar (optional), salt, and pepper to enhance the caramelization process. Stir occasionally.

Prep the Sauce & Arugula

Mix the horseradish sauce and mayonnaise in a small bowl. Adjust the ratio to your preferred level of spiciness. Set aside.
Toss the arugula with the olive oil and lemon juice until well coated. Set aside.

Assemble the Sandwich

Preheat a grill pan or skillet over medium heat. (Alternatively, you can use a toaster or oven to toast the bread.) Butter one side of each slice of bread and toast it until it's golden in the pan.
Spread the horseradish-mayo sauce on the untoasted side of one slice of bread. Layer the thinly sliced prime rib and provolone or Swiss cheese on top (if using). On the other slice of bread, spread the caramelized onions.
Put the two slices of bread together with the spreads and fillings inside. Cut the sandwich in half, and serve it with your favorite sides like coleslaw, pickles, or potato chips.

Serving with Au Jus (Optional)

Heat the reserved juices from the cooked prime rib in a small saucepan. If needed, add a bit of beef broth to adjust the consistency. Season the au jus with salt and pepper to taste. Serve on the side with the sandwiches and use for dipping.

Notes

Choose the Right Bread: Select a sturdy bread like a baguette or ciabatta that can hold up to the juicy meat and toppings.
Balance Flavors: Consider the balance of flavors and textures in your sandwich. Sweet, tangy, creamy, and crunchy elements can all enhance the experience.
Layering Matters: Arrange the ingredients thoughtfully. Place condiments and spreads on the bread’s interior to prevent sogginess, and evenly distribute the prime rib, cheese, and vegetables for each bite.
Sauce Placement: If using au jus or another sauce, consider dipping it on the side to prevent the bread from getting too soggy.
Toast the Bread: Toasting the bread adds a delightful crunch and helps keep it from becoming overly soft from the sandwich fillings.

Nutrition