https://www.anediblemosaic.com/buffalo-beef-on-weck-recipe/

A Beef on Weck is a Buffalo tradition. (And at least in my family, we always pronounced it Beef on "Wick"!) In this hearty meat-stuffed sandwich, thinly sliced roast beef is piled high on a coarse salt and caraway seed-topped Kummelweck roll. A side of au jus for dipping is a must, and prepared horseradish is optional.

There are a number of local Buffalo restaurants that have a killer Beef on Weck. And there’s even a Beef on Weck trail throughout the area! I remember my dad always singing the praises of Charlie the Butcher. My personal favorite has always been Schwabl’s, which I grew up right down the street from. However, you’re likely to get a solid Beef on Weck almost anywhere you go in the Western New York area!

But for those of us who moved out of the area and are craving a little
bit of home, as well as a great beef sandwich, I dedicate this recipe
to you.

Kimmelweck Rolls:
Kaiser rolls
Egg white lightly beaten with water to make an eggwash
Coarse kosher salt
Caraway seeds
Horseradish Sauce:
Mayo
Prepared horseradish
Sour cream
Buttermilk
Worcestershire sauce
Garlic powder
Black pepper
Beef:
Beef consommé
Deli-sliced roast beef

Step-by-Step Instructions
How to Make Kimmelweck Rolls From Kaiser Rolls:
how to make kummelweck rolls from kaiser rolls
Preheat the oven to 300F. Line a baking tray with a silpat baking mat or parchment paper. Place the Kaiser rolls on the prepared tray. Lightly brush the tops with eggwash.
Sprinkle on the salt.
And now the caraway seeds.
Bake the rolls for 7 minutes.
How to Heat Sliced Roast Beef in Consommé:
heating sliced beef in au jus
Add the beef consommé to a small saucepan over medium heat.
Once simmering, add the beef (working in batches) to the liquid to warm it up, about 2 minutes.
piling beef on sandwich
Tips
After you transform a Kaiser roll into a Kimmelweck roll, I recommend eating it the same day for maximum freshness.
Only heat as much beef as you plan on eating to avoid having to keep re-heating it.
Once you assemble the sandwiches, serve them immediately. Otherwise, the au jus that’s on the beef can make them soggy.