Gluten-Free Butternut Squash, Cannellini, and Mushroom Gratin

Ingredients

• 4 tablespoon sextra-virgin olive oil , divided
• 1 leek , white and light-green parts only, halved lengthwise, slice d thin, and washed thoroughly
• 4 garlic clove s , slice d thin
• 8 ounce scremini mushrooms , stemmed and slice d thin
• 4 fresh sage leaves , slice d thin
• 1 tablespoon fresh thyme leaves
• \1 1/2 teaspoon stable salt , divided
• 3/4 teaspoon pepper , divided
• 1/4 teaspoon red pepper flakes
• 3 tablespoon sbrown rice flour
• 2 cup swhole milk
• 1 (15-ounce) can can nellini beans , rinsed
• 8 ounce skale , stemmed and cut into 1-inch piece s
• 1/2 teaspoon ground nutmeg
• 2 pound sbutternut squash , peeled, seeded, and cut into 1-inch piece s (6 cup s)
• 3/4 cup gluten-free panko bread crumbs
• 5 ounce sGruyère cheese , shredded (\1 2/3 cup s)

Instructions

1. 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.
2. 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.
3. 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.
4. Toss 6 cups peeled, seeded, and chopped butternut squash (1 inch pieces); remaining ¾ teaspoon salt; and remaining ¼ teaspoon pepper in large bowl.
5. Add mushroom mixture to bowl with squash and fold to combine.
6. Grease 13 by 9 inch baking dish; transfer mixture to prepared baking dish.
7. Stir ¾ cup gluten free panko style breadcrumbs and remaining 1 tablespoon oil in bowl until combined.
8. Add 1⅔ cups shredded Gruyère to bowl with panko and stir to combine.
9. Sprinkle panko mixture evenly over casserole
10. 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.