Classic Roast Beef Sandwich with Homemade Au Jus and Caramelized Onions

Name: Classic Roast Beef Sandwich with Homemade Au Jus and Caramelized Onions
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Yield: 4 servings
Cuisine: American
Ingredients: 12 oz Leftover roast beef, thinly sliced; 4 rolls Sandwich rolls (kaiser or French), split; 2 medium Yellow onions, thinly sliced; 2 tbsp Unsalted butter; 1 tbsp Olive oil; 2 cups Beef broth (low-sodium preferred); 0.25 cup Dry red wine (or additional beef broth); 1 tbsp Worcestershire sauce; 4 slices Provolone cheese slices

A hearty, savory roast beef sandwich topped with sweet caramelized onions and melted provolone, served with a rich homemade au jus for dipping. Perfect for turning leftover roast beef into an elevated snack or casual meal.

0.0(0 reviews)

Prep: 10m · Cook: 35m · Total45 mins

DifficultyMedium

Serves4

AuthorJake

Classic Roast Beef Sandwich with Homemade Au Jus and Caramelized Onions

Jake's note

"This sandwich shines when you want a comforting, restaurant-style bite from leftovers; the homemade au jus is the secret that turns simple ingredients into something special. It’s great for game day, quick dinners, or a weekend treat."

Classic Roast Beef Sandwich with Homemade Au Jus and Caramelized Onions

This roast beef sandwich is built on a simple principle: treat each component with intention. Thinly sliced leftover roast beef is warmed gently in a flavorful au jus so it stays tender instead of drying out; sweet, slowly caramelized onions lend an almost jammy counterpoint and provolone provides a melty, slightly nutty blanket. Using sturdy sandwich rolls that are lightly toasted keeps the assembly from collapsing into sogginess while still letting you tear into warm, juicy layers with each dip into the au jus.

What makes this version work is the orchestration of temperature and timing — onions cooked low and long, beef heated just enough to take the chill off in a savory bath, and cheese melted seconds before serving. The au jus is a small, punchy sauce (red wine and Worcestershire for depth) rather than a syrupy gravy, so it enhances without overpowering. This is a great weekend lunch or a way to elevate holiday roast leftovers into something celebratory yet relaxed; it’s equally at home beside a bowl of fries for casual company or plated with a crisp salad for a more composed meal.

Plan your timing

Enter your target meal time:

6:10 pm–6:19 pm→Caramelize the onions

6:19 pm–6:28 pm→Make the au jus and warm the beef

6:28 pm–6:37 pm→Prepare and toast the rolls

6:37 pm–6:46 pm→Assemble and melt the sandwiches

6:46 pm–6:55 pm→Serve with au jus for dipping

Ingredients

Yield

Instructions

Caramelize the onions

Heat butter and olive oil in a large skillet over medium-low heat. Add the thinly sliced onions and a pinch of salt, then cook gently, stirring every few minutes, until deep golden and sweet, about 25–30 minutes; adjust heat to prevent burning.

For this step

2 mediumYellow onions, thinly sliced
2 tbspUnsalted butter
1 tbspOlive oil

Make the au jus and warm the beef

In a small saucepan, add red wine and simmer 1–2 minutes to reduce slightly, then add beef broth and Worcestershire sauce and simmer 5–7 minutes to marry the flavors. Add the sliced roast beef to the simmering au jus just to warm through (30–60 seconds) so it stays tender; keep the au jus hot for serving.

For this step

12 ozLeftover roast beef, thinly sliced
2 cupsBeef broth (low-sodium preferred)
0.25 cupDry red wine (or additional beef broth)
1 tbspWorcestershire sauce

Prepare and toast the rolls

Preheat broiler or oven to 375°F (190°C). Split the rolls and place cut-side up on a baking sheet; toast in the oven or under the broiler for 2–4 minutes until lightly golden. Remove and keep warm.

For this step

4 rollsSandwich rolls (kaiser or French), split

Assemble and melt the sandwiches

Pile warmed roast beef on the bottom halves of toasted rolls, top with a generous spoonful of caramelized onions and a slice of provolone. Return sandwiches to the oven or place under the broiler for 1–2 minutes until the cheese melts and edges are bubbly.

For this step

4 slicesProvolone cheese slices

Serve with au jus for dipping

Transfer the au jus to small individual dipping bowls and serve alongside the assembled sandwiches so each person can dip as desired. Enjoy immediately while hot for the best texture and flavor.

Tips from the kitchen

Slice onions uniformly

Cut onions into evenly thin slices so they caramelize at the same rate and you avoid burnt edges or raw centers.

Low-and-slow caramelizing

Cook onions on medium-low and resist frequent stirring; patience concentrates sugars and develops deep color without burning.

Warm beef briefly

Drop the roast beef into simmering au jus for only 30–60 seconds to warm through — any longer and thin slices will overcook and toughen.

Toast rolls properly

Toast cut-side up until just golden to create a moisture barrier; under the broiler, keep the pan a rack below the element to prevent scorching.

Use pan juices if available

If you have roast drippings, skim fat and add a spoonful to the au jus for extra depth and an authentic roast flavor.

Variations & substitutions

French dip classic

Use a long hoagie roll and swap provolone for thinly sliced Swiss; add a splash of soy sauce to the au jus for extra umami.

Horseradish kick

Stir prepared horseradish into softened butter and spread on the rolls before toasting for a bright, spicy edge that pairs beautifully with beef.

Mushroom seitan substitute

For a vegetarian take, replace beef with thinly sliced, well-seasoned seitan or sautéed cremini mushrooms and use vegetable broth in the au jus.

Cheesy swap

Switch provolone for aged Gruyère or sharp cheddar for a nuttier, more assertive melt that stands up to robust onions and au jus.

Storage & make-ahead

Store leftover components separately: au jus in an airtight container in the refrigerator for up to 3–4 days, caramelized onions for 4–5 days, and sliced roast beef for 2–3 days. Reheat beef gently in the au jus over low heat just until warmed to avoid drying; reheat assembled sandwiches in a 350°F oven wrapped loosely in foil for 8–10 minutes to melt cheese without making the roll soggy.

What to serve with it

Serve each sandwich with a small bowl of au jus for dipping and a scattering of extra caramelized onions on top. Crisp shoestring fries, a sharp vinegary coleslaw, or dill pickles cut the richness nicely, while an amber ale or a medium-bodied red like a Merlot complements the beef and caramelized sweetness.

Frequently asked questions

Can I use freshly roasted beef instead of leftovers?

Yes — let the roast rest and slice it very thinly across the grain, then warm the slices briefly in the au jus; overcooking fresh slices will make them tough, so heat sparingly.

How do I make the au jus richer without wine?

Add a tablespoon of reduced balsamic or a teaspoon of tomato paste sautéed briefly, or use a splash of Worcestershire and a spoonful of pan drippings to deepen flavor without wine.

My rolls got soggy — how do I prevent that?

Toast the cut sides until golden to form a barrier and assemble just before serving; reserve some au jus for dipping rather than pouring inside the sandwich.

Can I thicken the au jus into a gravy?

Yes — whisk a cornstarch slurry (1 tsp cornstarch + 1 tbsp water) into simmering au jus and cook until slightly thickened, but keep it light if you want a true dipping jus.

Is there a shortcut for caramelized onions?

You can speed things up by adding a pinch of baking soda to the onions to accelerate browning, but use sparingly (a pinch) as it changes flavor; otherwise cook low and slow for the best result.

About the author

Jake

Hello, I'm Jake. I started this recipe site with the idea that I hated recipe websites that overwhelm you with long stories and ads just to see plain content that's not helpful. My goal is to provide you with quality recipes, simple ideas and a fun cooking experience. There's lots of fun things to cook, and I think as you browse the site you'll find that TopShelf.Recipes is the place for quality recipes on the web.

See all recipes by Jake →

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Ingredients

4 servings

Step 1: Caramelize the onions

Yellow onions, thinly sliced2 medium
Unsalted butter2 tbsp
Olive oil1 tbsp

Step 2: Make the au jus and warm the beef

Leftover roast beef, thinly sliced12 oz
Beef broth (low-sodium preferred)2 cups
Dry red wine (or additional beef broth)0.25 cup
Worcestershire sauce1 tbsp

Step 3: Prepare and toast the rolls

Sandwich rolls (kaiser or French), split4 rolls

Step 4: Assemble and melt the sandwiches

Provolone cheese slices4 slices

Nutrition Facts

Per serving: 1 sandwich (420g)

Calories776

Total Fat38.8g

Saturated Fat16g

Trans Fat0g

Polyunsaturated Fat3.2g

Monounsaturated Fat13.6g

Total Carbohydrates64g

Dietary Fiber19.4g

Total Sugars3.4g

Protein45.6g

Nutrition values are estimated from USDA ingredient data and may vary based on preparation, brands, and portion sizes. Values are provided for informational purposes only.

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