How to Make It
Drain tuna, reserving 2 tablespoons oil. Combine tuna, reserved oil, celery, 3 tablespoons basil, and next 5 ingredients (through black pepper) in a medium bowl; toss to coat. Fold in eggs. Top each bread slice with about 3 tablespoons avocado, 2 tablespoons arugula, and 3/4 cup tuna mixture. Garnish toasts with remaining 1 tablespoon basil.