Place 16 ounces garbanzo beans, 1/3 cup finely chopped yellow onion, 1 egg, 3/4 cup grated gruyere cheese, 4 tablespoons chopped parsley, 1 minced garlic clove, and 1 tablespoon olive oil in the bowl of a food processor. Pulse until the mixture forms a thick, cohesive paste, scraping down the sides as needed.

Transfer the paste to a bowl, add 1/2 cup breadcrumbs, season with salt and pepper to taste, and mix until combined. Let the mixture rest for 10 minutes.

While the mixture rests, make the tahini sauce: in a small bowl whisk together 2 tablespoons tahini sauce, 2 tablespoons hot water, 1 tablespoon olive oil, 1 tablespoon lemon juice, 1 minced garlic clove, 2 tablespoons finely chopped Italian parsley, and salt and pepper to taste. Set the sauce aside.

Slightly wet your hands. Scoop about one tablespoon (or use an ice cream scooper) of the garbanzo mixture, roll it into a ball, then gently flatten into a small patty. Repeat until all mixture is formed into croquettes.

Heat 2 tablespoons olive oil in a large skillet over medium heat until shimmering. Add croquettes in a single layer without overcrowding the pan (cook in batches if necessary).

Fry the croquettes about 2 minutes per side, or until golden brown and heated through, turning carefully with a spatula.

Transfer cooked croquettes to a paper towel-lined plate to drain any excess oil. Serve warm with the tahini sauce.