Lay the bread slices on a work surface. Spread each slice with a thin layer of horseradish. Top 4 of the bread slices with the roast beef slices and the chives, dividing them evenly, and season with salt and pepper. Arrange a lettuce leaf over the roast beef. Top with the remaining 4 bread slices and press firmly.
Using a serrated knife, cut off the crusts from each sandwich, then cut e