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sandwich with leftover prime rib and caramelized onions

Leftover Prime Rib Sandwich

A Leftover Prime Rib Sandwich is the best way to enjoy your prime rib roast leftovers. This recipe details how to make the best prime rib sandwich!
Course Main Course
Cuisine American
Prep Time 5 mins
Cook Time 15 mins
Total Time 20 mins
Servings 4 sandwiches
Calories 783


  • 2 tablespoon butter
  • 2 large yellow onions (sliced thin)
  • 2 tablespoon mayonnaise
  • 1 teaspoon creamy horseradish
  • 16 cloves roasted garlic
  • 2 cups arugula
  • 1 teaspoon olive oil
  • 1 teaspoon white balsamic vinegar (or lemon juice)
  • 8 slices sourdough (or large baguette, sliced)
  • 12 ounces prime rib (sliced thin)


  • To caramelize onions, melt butter in skillet over medium high heat. Add sliced onions, arrange in single layer, and don't stir until they start to brown. Gradually reduce heat to prevent burning and only stir when they start to brown too much. Continue cooking until a dark caramel color forms. Set aside.
  • To make spread, combine mayonnaise and horseradish. I chose to set my roasted garlic cloves directly on the sandwich but you can mash and mix with the horseradish mayo, if you prefer.
  • In small bowl, dress arugla greens with olive oil and vinegar. Season with salt and pepper, if desired.
  • To serve, layer sandwich with spread, dressed arugula, prime rib and caramelized onions. Serve cold.


Makes 4 sandwiches


Calories: 783kcal | Carbohydrates: 83g | Protein: 28g | Fat: 37g | Saturated Fat: 14g | Cholesterol: 69mg | Sodium: 802mg | Potassium: 546mg | Fiber: 4g | Sugar: 7g | Vitamin A: 415IU | Vitamin C: 11.4mg | Calcium: 118mg | Iron: 6.4mg