In a mixing bowl, add the drained and rinsed chickpeas. Using a fork, mash the chickpeas until they are mostly broken down but still have some texture. This will help bind the salad together while providing a hearty base.

Add the finely chopped celery, red onion, red bell pepper, and parsley to the mashed chickpeas. These ingredients add crunch and freshness to the salad.

In a small bowl, whisk together the lemon juice, vegan mayonnaise, Dijon mustard, garlic powder, salt, and black pepper until smooth. This dressing will enhance the flavors of the salad.

Pour the dressing over the chickpea mixture and stir until everything is well combined. Taste and adjust seasoning if necessary.

Lay out 4 slices of whole grain bread on a clean surface. This will be the base of your sandwiches.

Spoon a generous amount of the chickpea salad onto each slice of bread, spreading it evenly.

Top the chickpea salad with mixed greens and tomato slices for added freshness and flavor.

Place the remaining slices of bread on top to complete the sandwiches. Press down gently to secure the filling.

Using a bread knife, cut each sandwich in half diagonally for easy eating.