Created by ForeverMama on November 7, 2017
Step 1: Position a rack in the center of the oven and heat to 400°F.
Step 2: Line a rimmed baking sheet with aluminum foil and lightly brush with oil. Put the squash cut side down on the sheet, and roast until fork tender, about 60 minutes. Set aside to cool. (Can be done a day or 2 ahead)
Step 3: Reduce the oven temperature to 350°F.
Step 4: Heat the milk in a medium saucepan over medium heat until bubbles form around the side of the pan, about 7 minutes. Remove the pan from the heat and cover.
Step 5: Melt the butter in a medium saucepan over medium heat. Add the flour, and whisk until smooth. continue to cook, whisking constantly without browning, for about 2 minutes. Whisking constantly, gradually add the milk and cook, continuing to whisk, until the sauce thickens, about 2 minutes. Remove 1 cup of the sauce, cover, and reserve. Remove the pan with the remaining sauce from the heat.
Step 6: Scoop the flesh from the squash into a medium bowl, and mash with a fork until free of lumps. Add the squash, 1/2 cup of the Parmigiano, the sage, nutmeg, 1 tsp. salt, and 1/4 tsp. pepper to the sauce in the pan, and season to taste with more salt and pepper. (Up to this point, this process can also be made ahead).
Step 7: Heat the 2 Tbs. of oil in a large skillet over medium heat. Add the onion and cook, stirring occasionally, until translucent, about 2 minutes.
Step 8: Add the garlic and cook until fragrant, about 30 seconds. Add the chard stems and cook, stirring occasionally, until they start to soften, about 3 minutes.
Step 9: Add the chard leaves in batches, stirring and allowing to wilt before adding another batch.
Step 10: Cook, stirring occasionally, until tender, about 6 minutes. Remove the pan from the heat, add the reserved 1 cup of sauce, 1/2 cup of the Parmigiano, 1/2 tsp. salt, and 1/4 tsp. pepper, and stir to coat the chard.
Step 11: In a medium bowl, combine the ricotta, egg, the remaining 1/2 cup of Parmigiano, 1/2 tsp. salt, and 1/4 tsp. pepper.
Step 12: Lightly oil a 9×13-inch baking dish. Evenly spread 1-1/4 cups of the squash sauce in the bottom of the dish. Cover with a layer of noodles, then layer in one-fourth of the remaining squash sauce, one-fourth of the chard mixture, and one-fourth of the fontina. Dollop one-fourth of the ricotta mixture on top. Beginning again with a layer of noodles, repeat the layering as directed above three more times.
Step 13: Bake until the edges of the lasagna are browned and bubbly, rotating the pan halfway through baking, 45 to 55 minutes.
Step 14: Heat the broiler on high. Broil for 1 to 2 minutes to brown the top. cool for about 15 minutes before serving.