Add the walnuts and chickpeas to a food processor and pulse until a coarse, crumbly mixture forms. Do not process to a paste.

Heat the olive oil in a wide skillet over medium-high heat. After 90 seconds, when the oil is hot, add the chickpea and walnut mixture. Sauté the broken bits of chickpeas and walnuts, stirring regularly for 6-7 minutes until lightly browned and beginning to crisp in spots.

Add the diced onion and garlic and cook over medium-high heat, stirring frequently for 2-3 minutes until fragrant.

Transfer the cooled mixture to a bowl and add the breadcrumbs and water. Firmly squeeze the contents of the bowl together until a firm meatball dough is formed.

With moistened hands, shape into even tablespoon-size balls, pressing firmly so they hold together.

Preheat the oven to 375°F (190°C). Arrange the meatballs on a parchment-lined baking pan lightly coated with oil, then drizzle with the remaining oil. Bake for 18 minutes, turn with a spatula, and continue baking for 6–8 minutes until browned and crisp on all sides.

Warm the marinara sauce in a separate pan over medium heat until heated through. Transfer the meatballs to the sauce and simmer briefly to coat. Serve warm over pasta or in a sub, garnished with chopped parsley.