This big baked corn, red pepper, lima and green bean casserole has a crispy, cheesy topping.
2 tablespoons unsalted butter
1/4 cup extra-virgin olive oil
1 small white onion, finely chopped
3 large garlic cloves, minced
1 large red bell pepper, finely chopped
3 cups fresh corn kernels (from 4 large ears)
1/2 pound green beans, cut into 1-inch lengths
3 cups cooked fava beans or frozen baby lima beans, thawed
1 teaspoon Aleppo pepper
Freshly ground black pepper
1/2 cup vegetable stock
2 tablespoons chopped basil
2 tablespoons finely chopped chives
1 cup heavy cream
2 large eggs, beaten
3/4 cup panko bread crumbs
4 ounces Gruyère cheese, shredded (1 cup)
Preheat the oven to 425° and position a rack in the center. In a large, deep skillet, melt the butter in 2 tablespoons of the oil. Add the onion and garlic and cook over moderate heat, stirring, until softened, 5 minutes. Add the bell pepper, corn, green beans, fava beans and Aleppo, season with salt and black pepper and cook, stirring, until the beans are crisp-tender, 3 minutes. Add the stock and simmer until evaporated, about 3 minutes.
Transfer the vegetables to a large baking dish and let cool slightly. Stir in the basil, chives, cream and eggs.
In a small bowl, toss the panko with the shredded cheese and the remaining 2 tablespoons of oil. Season the topping with salt and pepper; sprinkle over the succotash and bake for 10 minutes, until heated through.
Turn on the broiler and broil in the center of the oven for about 3 minutes, just until the top is golden. Let the gratin stand for 10 minutes, then serve.
The finished gratin can be refrigerated overnight. Reheat before serving.