Gluten-Free Butternut Squash, Cannellini, and Mushroom Gratin
By Aran GoyoagaPublished on November 5, 2025
Time
2 hours
Yield
Serves 6 to 8
Ingredients
4 tablespoons extra-virgin olive oil, divided1 leek, white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly4 garlic cloves, sliced thin8 ounces cremini mushrooms, stemmed and sliced thin4 fresh sage leaves, sliced thin1 tablespoon fresh thyme leaves 1½ teaspoons table salt, divided¾ teaspoon pepper, divided¼ teaspoon red pepper flakes 3 tablespoons brown rice flour 2 cups whole milk 1 (15-ounce) can cannellini beans, rinsed8 ounces kale, stemmed and cut into 1-inch pieces½ teaspoon ground nutmeg 2 pounds butternut squash, peeled, seeded, and cut into 1-inch pieces (6 cups)¾ cup gluten-free panko bread crumbs 5 ounces Gruyère cheese, shredded (1⅔ cups)
Before You Begin
We developed this recipe to be gluten-free, but you can substitute an equal amount of all-purpose flour for the brown rice flour and standard panko for the gluten-free panko. For a vegan version, use oat milk in place of whole milk and cheddar-style vegan cheese.
Instructions
- Adjust oven rack to middle position and heat oven to 400 degrees. Combine 3 tablespoons extra-virgin olive oil, 1 leek (white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly), and 4 thinly sliced garlic cloves in 12-inch skillet. Cook over medium heat, stirring occasionally, until leeks soften but are not browned, about 5 minutes.
- Stir in 8 ounces thinly sliced cremini mushrooms, 4 thinly sliced sage leaves, 1 tablespoon thyme leaves, ¾ teaspoon table salt, ½ teaspoon pepper, and ¼ teaspoon red pepper flakes. Cook, stirring occasionally, until mushrooms soften and begin to brown, about 6 minutes.
- Stir in 3 tablespoons brown rice flour until incorporated, about 30 seconds. Gradually stir in 2 cups whole milk. Continue to cook, stirring often, until sauce has thickened, about 5 minutes. Remove skillet from heat and stir in 1 can rinsed cannellini beans; 8 ounces kale, stemmed and cut into 1-inch pieces; and ½ teaspoon ground nutmeg.
- Toss 6 cups peeled, seeded, and chopped butternut squash (1-inch pieces); remaining ¾ teaspoon salt; and remaining ¼ teaspoon pepper in large bowl. Add mushroom mixture to bowl with squash and fold to combine. Grease 13 by 9-inch baking dish; transfer mixture to prepared baking dish. Stir ¾ cup gluten-free panko-style breadcrumbs and remaining 1 tablespoon oil in bowl until combined. Add 1⅔ cups shredded Gruyère to bowl with panko and stir to combine. Sprinkle panko mixture evenly over casserole
- Cover dish with aluminum foil and bake until squash is tender, about 40 minutes. Remove foil and bake until top is golden brown, about 15 minutes longer. Let gratin sit for 10 minutes before serving.
Time
2 hoursYield
Serves 6 to 8Ingredients
4 tablespoons extra-virgin olive oil, divided
1 leek, white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly
4 garlic cloves, sliced thin
8 ounces cremini mushrooms, stemmed and sliced thin
4 fresh sage leaves, sliced thin
1 tablespoon fresh thyme leaves
1½ teaspoons table salt, divided
¾ teaspoon pepper, divided
¼ teaspoon red pepper flakes
3 tablespoons brown rice flour
2 cups whole milk
1 (15-ounce) can cannellini beans, rinsed
8 ounces kale, stemmed and cut into 1-inch pieces
½ teaspoon ground nutmeg
2 pounds butternut squash, peeled, seeded, and cut into 1-inch pieces (6 cups)
¾ cup gluten-free panko bread crumbs
5 ounces Gruyère cheese, shredded (1⅔ cups)
Ingredients
4 tablespoons extra-virgin olive oil, divided
1 leek, white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly
4 garlic cloves, sliced thin
8 ounces cremini mushrooms, stemmed and sliced thin
4 fresh sage leaves, sliced thin
1 tablespoon fresh thyme leaves
1½ teaspoons table salt, divided
¾ teaspoon pepper, divided
¼ teaspoon red pepper flakes
3 tablespoons brown rice flour
2 cups whole milk
1 (15-ounce) can cannellini beans, rinsed
8 ounces kale, stemmed and cut into 1-inch pieces
½ teaspoon ground nutmeg
2 pounds butternut squash, peeled, seeded, and cut into 1-inch pieces (6 cups)
¾ cup gluten-free panko bread crumbs
5 ounces Gruyère cheese, shredded (1⅔ cups)
Ingredients
4 tablespoons extra-virgin olive oil, divided
1 leek, white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly
4 garlic cloves, sliced thin
8 ounces cremini mushrooms, stemmed and sliced thin
4 fresh sage leaves, sliced thin
1 tablespoon fresh thyme leaves
1½ teaspoons table salt, divided
¾ teaspoon pepper, divided
¼ teaspoon red pepper flakes
3 tablespoons brown rice flour
2 cups whole milk
1 (15-ounce) can cannellini beans, rinsed
8 ounces kale, stemmed and cut into 1-inch pieces
½ teaspoon ground nutmeg
2 pounds butternut squash, peeled, seeded, and cut into 1-inch pieces (6 cups)
¾ cup gluten-free panko bread crumbs
5 ounces Gruyère cheese, shredded (1⅔ cups)
Why This Recipe Works
This cozy gratin can be a main course accompanied by a green salad, or it can be a hearty, luscious side for a winter meal or a holiday table. We sautéed leeks, garlic, mushrooms, sage, and thyme to use as a flavor base for a gluten-free bechamel, adding milk and brown rice flour as the thickener. We stirred cannellini beans and chopped kale into the sauce, folded it in with diced butternut squash, and then poured the whole mixture into a casserole dish. Cutting the squash and kale into 1-inch pieces ensured that they would cook in a relatively short time. A topping of grated Gruyère mixed with gluten-free panko breadcrumbs brought nutty flavor and a crisp texture that complemented the tenderness of the vegetables.
Before You Begin
We developed this recipe to be gluten-free, but you can substitute an equal amount of all-purpose flour for the brown rice flour and standard panko for the gluten-free panko. For a vegan version, use oat milk in place of whole milk and cheddar-style vegan cheese.
Instructions
- Adjust oven rack to middle position and heat oven to 400 degrees. Combine 3 tablespoons extra-virgin olive oil, 1 leek (white and light-green parts only, halved lengthwise, sliced thin, and washed thoroughly), and 4 thinly sliced garlic cloves in 12-inch skillet. Cook over medium heat, stirring occasionally, until leeks soften but are not browned, about 5 minutes.
- Stir in 8 ounces thinly sliced cremini mushrooms, 4 thinly sliced sage leaves, 1 tablespoon thyme leaves, ¾ teaspoon table salt, ½ teaspoon pepper, and ¼ teaspoon red pepper flakes. Cook, stirring occasionally, until mushrooms soften and begin to brown, about 6 minutes.
- Stir in 3 tablespoons brown rice flour until incorporated, about 30 seconds. Gradually stir in 2 cups whole milk. Continue to cook, stirring often, until sauce has thickened, about 5 minutes. Remove skillet from heat and stir in 1 can rinsed cannellini beans; 8 ounces kale, stemmed and cut into 1-inch pieces; and ½ teaspoon ground nutmeg.
- Toss 6 cups peeled, seeded, and chopped butternut squash (1-inch pieces); remaining ¾ teaspoon salt; and remaining ¼ teaspoon pepper in large bowl. Add mushroom mixture to bowl with squash and fold to combine. Grease 13 by 9-inch baking dish; transfer mixture to prepared baking dish. Stir ¾ cup gluten-free panko-style breadcrumbs and remaining 1 tablespoon oil in bowl until combined. Add 1⅔ cups shredded Gruyère to bowl with panko and stir to combine. Sprinkle panko mixture evenly over casserole
- Cover dish with aluminum foil and bake until squash is tender, about 40 minutes. Remove foil and bake until top is golden brown, about 15 minutes longer. Let gratin sit for 10 minutes before serving.
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