Roast beef spinach sandwiches

Large sub bread

Roast beef

Fresh baby spinach

Cheddar cheese slices cut on the diagonal 

Sauce:

3/4 cup good mayonnaise

1 1/2 tablespoons Dijon mustard

1 tablespoon whole-grain mustard

1/2 tablespoon prepared horseradish

2 tablespoons sour cream

Kosher salt

Assemble the sandwiches by cutting open bread and slathering it generously with sauce. Add cheese, beef and finally spinach. Close bread and slice. Serve cold.