For the roast beef and sandwich:
- 3–4 pounds eye of round or tenderloin roast, at room temperature
- Salt and pepper, to taste
- Horseradish, for garnish
- Mustard, for garnish
For the kimmelweck rolls:
- 1 tablespoon coarse salt
- 1 tablespoon whole caraway seeds
- 1 tablespoon cornstarch
- 1/4 cup warm water
- 1/2 cup boiling water
- 6 Kaiser rolls, sliced
To prepare the meat:
- Preheat oven to 450 degrees F.
- Position a shallow grate on a roasting pan filled with 1/4-inch of water. Place the roast on the grate fat side up. Sprinkle generously with salt and pepper.
- Place the roast in the oven, and lower oven temperature to 350 degrees F.
- Cook until a meat thermometer inserted into the center of the roast reads 130 degrees F, about 10-20 minutes per pound.
- Remove the roast from the oven, and cover loosely with foil.
- Allow the covered roast to rest for 10-15 minutes.
- Pour the gravy from the roasting pan into a large Pyrex measuring cup.
- Add water to the gravy mixture until it is 1/3 gravy juice and 2/3 water to make the au jus for the sandwiches.
To prepare the rolls:
- In a shallow pan or pie tin, combine the salt and caraway seeds.
- In a small saucepan, boil 1/2 cup water. In a small bowl, dissolve the cornstarch in the warm water. Add the cornstarch mixture to the boiling water. Return the mixture to a boil until it is thick enough to coat a spoon. Remove from heat, and allow to cool.
- Preheat oven to 350 degrees F.
- On a baking sheet, position the 12 Kaiser roll halves.
- Brush the top of each roll with the cornstarch solution. Sprinkle each top with the salt and kimmelweck mixture.
- Bake rolls until the kimmelweck dries, about 4-5 minutes.
To assemble the sandwiches:
- Slice the warm roast beef as thin as possible.
- Lightly dip the top half in the au jus only enough to moisten it.
- Pile 4 ounces of sliced beef onto the bottom of the roll.
- Add horseradish and mustard.
- Finish the sandwich by capping with the top half of the roll.