In a bowl, stir together mayonnaise, soy sauce, sugar, and lemon juice. Stir in wasabi paste.
Layer 4 slices of pumpernickel or whole wheat bread with a thin layer of wasabi mayo. Top 2 of the pieces of bread with 3 slices of roast beef. Top the beef with chopped chives, followed by the remaining coated bread slices.
Cut into 4 rectangles and tie each mini sandwich with a whole chive.