Chickpea Veggie Burgers

Name: Chickpea Veggie Burgers
Ingredients: 2 15-oz. cans chickpeas, drained and rinsed; .50 cup jarred harissa (such as Mina), plus more for serving (optional); 1 cup loosely packed fresh cilantro leaves and/or flat-leaf parsley leaves, finely chopped; .50 cup panko; 1 tablespoon fresh lemon juice (from 1 lemon); 1.50 teaspoons kosher salt; Freshly ground black pepper; 2 tablespoons olive oil; 2 avocados; 4 brioche buns, split and toasted; Sliced tomatoes, sliced red onion, and red leaf lettuce, for topping