Start by draining and rinsing your chickpeas well to remove excess salt and starch. Add them to a bowl and mash them using a fork or masher until mostly broken but still slightly chunky. This texture helps the sandwich feel hearty and satisfying.
In the same bowl, add gochujang, vegan mayo, soy sauce, rice vinegar, maple syrup, and garlic powder. Mix everything thoroughly so the flavors combine into a creamy, spicy dressing. Make sure the chickpeas are evenly coated.
Now fold in the chopped onion, celery, and green onions. These ingredients add a fresh crunch and balance the creamy texture. Mix gently so everything is well distributed without over-mashing.
Take your bread slices and layer lettuce leaves on one side to prevent sogginess. Spoon the chickpea mixture generously over it and spread evenly. Add cucumbers or tomatoes if you like extra freshness.
Top with another slice of bread and press gently. Slice in half and serve immediately for the best texture and flavor. You can also chill the filling slightly before serving if you prefer a cooler sandwich.