1 pound zucchini or summer squash, peeled and thinly sliced
1 pound combined of fennel and leek, rinsed and drained, and thinly sliced
6 tablespoons olive oil or unsalted butter
1 large onion, chopped
2 garlic cloves, finely chopped (optional)
2 cups milk, stock, or cooled vegetable cooking liquid
¼ cup all-purpose flour
salt and freshly milled black pepper
1 ¼ cups grated cheddar, swiss, muenster, monterey jack, or other cheese
½ cup fresh bread crumbs or panko
Preheat the oven to 375°F. Lightly grease a 2-quart gratin or shallow baking dish. Heat 2 tablespoons of the oil in a skillet over medium heat. Saute the leeks for a few minutes until translucent. Add the fennel and summer squash and cook until crisp-tender (these will continue cooking in the oven). In a separate skillet, heat 2 more tablespoons of oil. Cook the onions and garlic, if using, until they start to brown, about 4 minutes. Whisk the milk into the flour in a small bowl. Whisk the milk mixture into the onion/garlic mixture and cook, stirring constantly, until the sauce is bubbly and thickened. Add salt and pepper to taste. Layer half of the squash, 1/3 of the sauce, ¼ cup of cheese and repeat, ending with 1 cup sauce and ½ cup cheese. Combine the bread crumbs and the remaining 2 tablespoons of oil. If using butter, melt the remaining 2 tablespoons before using. Sprinkle crumbs over the cheese. Bake for 25-30 minutes, until the top is well browned.