Most gratins need milk and cheese to add flavor and richness, but for this butternut squash gratin, we wanted the sweet, nutty flavor and brilliant color of the squash to shine. We cut the squash into bite-size pieces to eliminate pre-cooking and then toss them with fruity extra-virgin olive oil, salt, pepper, and thyme. Caramelizing the onions before layering them with the squash not only deepens their flavor but also gets rid of excess moisture so the squash doesn’t taste steamed or waterlogged. To add crunch, we top with casserole with a mixture of toasted panko near the end of baking and then finish the dish with a fresh chopped parsley.
Prep Time: 15 minutes
6 tablespoons good quality extra-virgin olive oil
1/4 cup gluten free panko or gluten free sourdough bread crumbs
Salt and pepper
2 pounds onions, halved and sliced thin
1/4 cup water
4 teaspoons chopped fresh sage
2 garlic cloves, minced
4 pounds butternut squash
1/4 cup minced fresh parsley
1 teaspoon grated lemon zest
Avoid buying prepeeled or chunked butternut squash for this dish.
Adjust oven rack to middle position and heat oven to 425 degrees. Grease 13 by 9-inch baking dish. Combine 1 tablespoon oil and gluten free panko in 12-inch skillet and toast over medium-high heat, stirring frequently, until golden brown, about 3 minutes. Transfer to bowl and stir in 1/2 teaspoon salt and 1/4 teaspoon pepper; set aside.
Heat 3 tablespoons oil in now-empty skillet over medium heat until shimmering. Add onions, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring frequently, until soft and golden brown, about 30 minutes. Add 2 tablespoons water and cook, scraping up any browned bits, until water is evaporated, about 5 minutes. Add remaining 2 tablespoons water and cook until onions are caramelized and water is evaporated, about 5 minutes longer. Add 2 teaspoons sage and garlic and cook until fragrant, about 30 seconds; set aside.
Trim ends from squash and peel. Cut in half lengthwise, then quarter each half lengthwise and remove seeds. Cut each piece into 1/4-inch-thick slices (you should have 11 cups). Toss squash, remaining 2 tablespoons oil, remaining 2 teaspoons sage, 1 teaspoon salt, and 3/4 teaspoon pepper together in large bowl. Arrange half of squash evenly in prepared dish. Spread half of onion mixture evenly over squash. Arrange remaining squash evenly over onion mixture. Spread remaining onion mixture evenly over squash.
Cover dish with aluminum foil and bake until squash is nearly tender, about 40 minutes. Sprinkle panko mixture over top and continue to bake, uncovered, until squash is tender, about 15 minutes longer. Transfer dish to wire rack. Combine parsley and lemon zest in bowl and sprinkle over gratin. Serve.
Adapted From America's Test Kitchen