Preheat your oven to 400°F (200°C). Lightly grease a 2-quart gratin dish or a 9x13-inch baking dish with a tablespoon of olive oil.
Spread the warm tomato sauce evenly across the bottom of the prepared dish. Spoon the cooked lima beans over the sauce and sprinkle lightly with salt and pepper.
Scatter the mozzarella cubes evenly over the beans, pressing them gently into the sauce.
Sprinkle the bread crumbs over the top, followed by the grated Parmesan cheese.
Drizzle the remaining olive oil over the crumb topping.
Bake for 20 to 30 minutes, or until the sauce is bubbly, the cheese is melted, and the bread crumbs are golden brown and crisp.
Remove from the oven and let it rest for a few minutes.
Garnish generously with fresh parsley and another grind of black pepper before serving.
Don't have lima beans? This recipe works beautifully with cooked cannellini beans, gigante beans, or even chickpeas.