How to Make It
Stir together first 4 ingredients; let stand 30 minutes.
Top 6 bread slices with roast beef; sprinkle with salt, if desired. Spread 1 1/2 tablespoons sour cream mixture over roast beef. Top evenly with bean sprouts, tomato, and dill pickle. Cover with remaining bread slices. Cut sandwiches in half diagonally, and serve immediately.