Leftover Pot Roast Sandwich

Ingredients

• 4La Brea Bakery frozen French dinner rolls, ready to bake
• 10 ml (2 teaspoons)olive oil
• 1yellow onion, sliced
• 360 ml (1½ cups)leftover pot roast, warmed
• 4 slicesSwiss cheese
• 60 ml (¼ cup)mayonnaise
• 5 ml (1 teaspoon)wholegrain mustard
• 5 ml (1 teaspoon)prepared horseradish

Instructions

1. 1

   Bake the rolls

   Heat the oven to 195°C (385°F). Put the rolls on a baking tray and bake according to the packet directions, then take them out of the oven.

2. 2

   Cook the onions

   Meanwhile, warm the olive oil in a non-stick frying pan over a medium-low heat. Add the sliced onion and toss to coat. Cook for 20–30 minutes, stirring now and then, until soft and golden brown.

3. 3

   Assemble and heat

   Halve the rolls and fill each with pot roast, caramelised onions and Swiss cheese. In a bowl, whisk the mayonnaise with the horseradish and mustard. Spread about 15 ml (1 tablespoon) of sauce on each sandwich. Wrap them in foil, or cover the baking tray tightly with foil, and return to the oven for 5–10 minutes, until the cheese has melted and the sandwiches are hot. Serve straight away.

What is a pot roast sandwich?

A pot roast sandwich puts tender, slow-cooked beef between pieces of bread, often with a rich sauce or savoury toppings. It belongs to the practical American tradition of turning a cooked roast into another meal.

This version pairs warmed leftover beef with sweet, slowly cooked onion, Swiss cheese and a sharp, creamy sauce. Baking the filled rolls briefly brings the layers together and warms them through.

Nutrition and macros by portion

The nutrition label shows one serving as written: 392 calories, 27g protein, 16g carbs, 24g fat.

The rolls provide most of the carbohydrates, while the beef contributes protein and the olive oil, cheese and mayonnaise contribute much of the fat. Pair a sandwich with a generous portion of salad or vegetables for a fresh contrast and a more balanced plate.

Choose the right leftovers

Pot roast: Use cooked beef that is tender enough to portion into the rolls. Warm it before assembling so the short final bake can focus on heating the sandwiches and melting the cheese.

Rolls: The recipe specifies frozen ready-to-bake French dinner rolls. Bake them according to their packet directions, as baking time can vary between products.

Take your time with the onions

Low heat: The onions cook for 20–30 minutes over a medium-low heat, softening and turning golden rather than browning too quickly. Stir occasionally so they cook evenly in the oil.

Doneness: Look for soft slices with a golden-brown colour. Their sweetness balances the beef and the sharper notes in the sauce.

Build a balanced sauce

Creamy base: Mayonnaise gives the sauce its body, while wholegrain mustard adds a savoury tang. Whisk them together with the prepared horseradish so the flavours are evenly distributed.

Even spread: About 15 ml (1 tablespoon) per sandwich gives each roll some sauce without needing to mix it into the beef. Keep the sauce inside the roll so it is easier to eat.

Melt the cheese gently

Foil cover: Wrapping the sandwiches, or tightly covering the tray, helps them heat through while the Swiss cheese melts. Bake for 5–10 minutes, checking that the rolls are hot and the cheese has melted.

Serve promptly: The rolls are best served straight from the oven, while the cheese is soft and the filling is warm.

What to serve alongside

Fresh contrast: A crisp green salad or crunchy raw vegetables pair well with the rich beef, cheese and mayonnaise-based sauce.

Something warm: Serve with a simple vegetable soup or roasted vegetables if you want a more substantial meal. Keep the sides straightforward so the filled rolls remain the focus.

Recipe notes & tips

• Warm the pot roast before filling the rolls so it heats through during the brief oven finish.
• Slice the onion evenly to help the pieces soften at a similar rate.
• Stir the onions occasionally, rather than constantly, as they cook over the medium-low heat.
• Whisk the sauce until the mustard and horseradish are spread evenly through the mayonnaise.
• Check the rolls' packet directions before baking, since products may differ.
• Start checking the sandwiches after 5 minutes in the oven and remove them once the cheese has melted and the filling is hot.

Variations

• Add pickles: Tuck sliced pickles into the assembled sandwich for a sharp, crunchy contrast.
• Use another cheese: Swap the Swiss for another cheese that melts well.
• Adjust the horseradish: Use less for a milder sauce or more for a stronger kick.
• Add greens: Place a handful of fresh leaves in the sandwich after baking.
• Try another roll: Use a similar soft dinner roll if the specified rolls are unavailable.

Common mistakes to avoid

• Rushing the onions: They may stay firm and pale; cook them over medium-low heat for the full 20–30 minutes.
• Using cold beef: The short final bake may not warm it enough; warm the pot roast before assembling.
• Overbaking the rolls: They can become too firm; follow the packet directions and remove them once baked.
• Leaving the tray uncovered: The tops may dry out during the final bake; wrap the sandwiches or cover the tray tightly with foil.
• Adding too much sauce: The filling can become messy; spread about 15 ml (1 tablespoon) on each sandwich.

How to store

Refrigerate leftover assembled sandwiches in a sealed container and eat within 2 days. Reheat covered with foil in the oven until hot throughout; the rolls may soften in storage. Keep any unused sauce covered and refrigerated.

Frequently asked questions