1. Combine avocado, wasabi, and lime juice; mash with a fork until smooth. Spread 1 tablespoon avocado mixture on 4 bread slices. Top with smoked salmon and red onion.
2. Top with 4 remaining bread slices; cut in half diagonally to form triangles. Spread one side of shorter edge of triangle with avocado mixture; dip edge into chives or sesame seeds, pressing to coat. Transfer to a platter; serve immediately.