Leftover Corned Beef Sandwich (The Gary Reuben)

The Gary Reuben is what happens when leftover corned beef stops being an afterthought.

We are not reheating slices in the microwave and calling it lunch. The meat gets crisped in a hot skillet until the edges caramelize. The bread gets butter-grilled and loaded with melted Swiss on one side and provolone on the other. And the sauce goes everywhere.

Leftover corned beef sandwich with Swiss, provolone, slaw, and Gary sauce on grilled rye bread

This is a crispy, saucy leftover corned beef sandwich loaded with melted cheese, a punchy slaw, and enough sauce to require napkins.

This is not a neat sandwich. It drips. It requires leaning over the plate. That is not a problem. That is the point.

If you made corned beef this week from my St. Patrick’s Day Kitchen Game Plan, this is the payoff meal.

Why This Sandwich Works

This sandwich wins because every part is doing a job.

Crispy corned beef gives you caramelized edges and real texture.
Butter-grilled bread gives the sandwich structure before it is even built.
Melted cheese on both sides brings flavor and helps hold everything together.
A flexible slaw lets you use kraut, cabbage, collards, or all three.
Gary Sauce pulls the whole thing together. Mixed into the slaw. Spread on the bread. Added again before closing. No holding back.

Real Talk

Let me be clear about what this sandwich is. You are not eating this in your car. You are not eating this over your laptop. The cheese stretches, the sauce drips down your wrist, and the slaw slides if you are not paying attention. That is not a flaw in the build. That is the whole identity. Messy over dry. Every time.

Crispy meat. Melty cheese. Saucy slaw. Butter-griddled bread. It's giving napkin energy, and I mean that as the highest compliment.

What Makes It a Gary Reuben

It starts with the sauce.

Not just a little swipe and call it done. The sauce gets mixed into the slaw and spread onto the bread too. Messy over dry. Always.

Then the corned beef gets crisped in the same pan you used for the bread, so nothing gets wasted and every bite picks up that buttery, salty, browned flavor.

And instead of stacking fillings on both slices and trying to wrestle it closed, you sauce both sides but build the meat and slaw on just one slice, then top it with the second. Less chaos. Better sandwich.

Gary Sauce Is the Hero

Everybody loves a great sauce. This one pulls the whole sandwich together.

It is creamy, tangy, smoky, a little sweet, and bold enough to stand up to crispy corned beef and melty cheese. Mix it into the slaw. Spread it on the bread. Add more before closing.

Do not be shy here.

Ingredients

For the Gary Sauce

½ cup mayonnaise
2 tablespoons ketchup
1 tablespoon Dijon mustard
1 tablespoon sweet pickle relish
1 teaspoon smoked paprika
½ teaspoon garlic powder
¼ teaspoon black pepper

For the Slaw

1 cup sauerkraut, squeezed dry
1 cup cooked collard greens, chopped, or chopped cabbage, or a mix of all three
2 to 3 tablespoons Gary Sauce, plus more to taste

For the Sandwiches

8 slices rye bread, or gluten-free bread if needed
Softened butter, for grilling
8 slices Swiss cheese
8 slices provolone cheese
About 1 pound leftover corned beef, sliced or chopped
1 to 2 tablespoons butter, for crisping the meat
Extra Gary Sauce, for spreading

Ingredients for Gary Reuben sandwiches including rye bread, Swiss cheese, provolone, leftover corned beef, cabbage, sauerkraut, collards, mayonnaise, ketchup, mustard, relish, butter, and spices

How to Make the Gary Reuben

1. Make the sauce

In a small bowl, stir together the mayonnaise, ketchup, Dijon, sweet pickle relish, smoked paprika, garlic powder, and black pepper until smooth.

Taste it. Then taste it again with the sandwich in mind. You want it punchy.

Mayonnaise, ketchup, mustard, relish, and spices in a bowl for making Gary Sauce

2. Make the slaw

In a medium bowl, combine the sauerkraut and your slaw base of choice. Use chopped cooked collards, chopped cabbage, or a mix of both. If using all three, aim for roughly equal parts sauerkraut, collards, and cabbage.

Add 2 to 3 tablespoons Gary Sauce and mix until evenly coated. Add more sauce if needed. The slaw should be dressed, not dry.

Mixed slaw with sauerkraut, cabbage, collards, and Gary Sauce lifted from a bowl

3. Grill the bread and melt the cheese

Heat a large skillet or griddle over medium heat.

Butter one side of each slice of bread. Place the bread butter-side down in the skillet. After a minute or two, flip each slice and immediately add Swiss to half the slices and provolone to the other half.

Let the cheese melt while the second side lightly toasts. Then transfer the slices to a plate or sheet pan, keeping them open-faced.

Swiss and provolone melting on toasted rye bread for Gary Reuben sandwiches

4. Crisp the corned beef

In the same skillet, add 1 to 2 tablespoons butter and turn the heat up to medium-high.

Add the leftover corned beef in an even layer. Let it sit long enough to actually brown. Then stir and keep cooking until you get plenty of caramelized edges.

Do not rush this part. This is where leftover corned beef turns into sandwich meat worth talking about.

Crispy slice of leftover corned beef ready for Gary Reuben sandwiches

5. Build the sandwich

Spread Gary Sauce on both cheese sides of the bread.

Pile the crispy corned beef onto one slice. Top with a generous amount of slaw.

Close the sandwich with the second slice of bread. If needed, secure each sandwich with 1 to 2 toothpicks before slicing.

You are still building the fillings on one side, not stacking both halves and trying to wrestle them together. Better control. Better structure. Same messy payoff.

Open-faced Gary Reuben with crispy corned beef, slaw, melted cheese, and sauce on grilled bread

6. Serve immediately

Slice in half and serve hot.

Napkins are not optional.

Tips for the Best Gary Reuben

Crisp the beef for real. Warmed through is not enough. You want browned edges and a little chew.
Squeeze the kraut well. Too much liquid will water down the slaw and make the bread soggy.
Use enough sauce. This sandwich is supposed to be messy. Lean into it.
Grill the bread before building. That toasted, buttery surface helps the sandwich hold up.
Melt the cheese directly on the bread. Swiss on one side, provolone on the other. That is part of the whole move.
Sauce both sides, build on one. Spread sauce on both cheese sides, but stack the meat and slaw on just one slice before closing. That gives you maximum flavor without assembly chaos.
Use whatever slaw base you have. Sauerkraut, cabbage, collards, or a mix. This recipe is flexible on purpose.
Use toothpicks before slicing if needed. They help hold everything together once the sandwich is fully loaded.

Slaw Options

This part is easy.

If you made collards earlier in the week, use them.

If you have sauerkraut in the fridge, use that.

If you want something fresher, add chopped cabbage.

If you want the best of all worlds, use all three and keep them roughly equal.

The sauce is what makes it all feel like one sandwich.

What to Serve With It

This sandwich can absolutely stand on its own, but if you want to make a full lunch out of it, here are a few good moves:

Kettle chips
Pickle spears
A simple side salad
Roasted potatoes
Leftover dressed cabbage if you have it

Storage and Make-Ahead Notes

The sauce can be made ahead and kept in the refrigerator for up to 4 days.

The slaw is best the day you make it, but it can hang out in the fridge for a few hours if needed.

Leftover corned beef keeps well in the refrigerator for 3 to 4 days. This sandwich is one of the best ways to use it up.

I would not assemble the sandwiches ahead. Make the components, then build fresh when you are ready to eat.

Half of a Gary Reuben sandwich showing corned beef, slaw, and melted cheese

Frequently Asked Questions

Can I make this gluten-free?

Yes. Use your favorite gluten-free bread and make sure your corned beef and sauerkraut are gluten-free too.

Do I have to use sauerkraut?

No. You can use chopped cabbage, cooked collards, or a mix of all three.

Can I skip one of the cheeses?

Yes, but I like the combo. Swiss brings the Reuben energy. Provolone makes it extra melty.

Can I use deli corned beef?

You can, but leftover home-cooked corned beef is the whole reason this sandwich hits like it does. If deli meat is what you have, use a generous pile and press it well in the hot skillet.

Can I use store-bought Thousand Island instead?

You can, but the homemade Gary Sauce is better here. It takes about 2 minutes to mix, and the smoked paprika and garlic powder to give it more depth than bottled dressing.

What if I do not have rye bread?

Sourdough is your best backup. It has enough structure and tang to work well here. Avoid soft white bread. This sandwich is too heavy and too saucy for that.

How do I use collard greens in the slaw?

Chop them finer if needed. Then squeeze out as much liquid as possible and toss them with the Gary Sauce just like you would with cabbage or sauerkraut. It is a different vibe than a classic Reuben, but it absolutely works.

Is the sauce spicy?

Not really. It has personality, not heat. The smoked paprika gives it depth more than spice.

More St. Patrick’s Day Recipes

Need the brisket first? Here are the methods that make this sandwich possible:

Did You Make This?

★ If you made this sandwich, leave a star rating below.
And if you added the toothpicks, leaned over the plate, and needed extra napkins, you did it right.

The Gary Reuben (Crispy Leftover Corned Beef Sandwich)