Tuscan Tuna-and-Bean Sandwiches

Ingredients
Method
Coarsely mash beans with a fork in a bowl, then stir in garlic, lemon juice, oil, parsley, salt, and pepper.
Flake tuna in a bowl with a fork, then stir in basil, olives, celery, onion, oil, lemon juice, salt, and pepper until combined.
Spoon one fourth of bean mixture on 1 slice of bread, then top with one fourth of tuna salad, some watercress, and a slice of bread. Make 3 more sandwiches in same manner.