Take the butternut squash and peel, seed, and cut it into 1/2-inch chunks.
Cook the lasagna noodles according to package directions.
Preheat oven to 450 degrees F.
In a large bowl, toss the butternut squash chunks with 1 tablespoon olive oil and 1/2 teaspoon salt, then place the chunks in a single layer on a large cookie sheet.
Roast the squash chunks for 30 minutes or until they're easily pierced with a fork, stirring after 15 minutes.
Remove chunks from the oven and mash squash with a food processor (or fork or potato masher) until almost smooth; set aside.
Lower the oven temperature to 375 degrees F.
In a large Dutch oven or saucepot, over medium heat melt together the remaining 1 tablespoon olive oil and 1 tablespoon of butter.
Add the chopped onion and cook for about 10 minutes or until golden, stirring often; add the Swiss chard and 1/4 teaspoon salt and cook until the chard is wilted and the liquid evaporates, which will take about 7 minutes.
Remove from heat and set aside.
In a large saucepan, melt the remaining butter over medium heat.
Whisk in the flour, pepper, garlic salt, nutmeg, thyme, and sage and cook for 1 minute while stirring constantly.
Gradually whisk in the milk until smooth and cook the sauce over medium-high heat until it boils and thickens slightly, stirring frequently.
Boil for an additional 2 minutes while stirring, then whisk in all but 2 tablespoons Parmesan cheese.
Remove the saucepan from heat.
In a 13" x 9" glass lasagna pan, spoon about 1/2 cup of the white sauce to cover the bottom of the pan.
Arrange 4 cooked lasagna noodles over the sauce, overlapping to fit; evenly spread all of the Swiss chard mixture over the noodles, top with about 1 cup white sauce, and sprinkle with about a 1/4 cup of mozzarella cheese.
Arrange 4 lasagna noodles on top, then about 1 cup white sauce and all butternut squash chunks, then a 1/4 cup of mozzarella cheese.
Top with remaining lasagna noodles, remaining white sauce, sprinkle with the chopped green onions and the remaining mozzarella cheese; sprinkle with the reserved 2 tablespoons Parmesan cheese.
Cover the lasagna pan with foil and bake at 375 degrees for 30 minutes, then remove the foil and bake for an additional 10 minutes or until hot and bubbly; let lasagna cool for 10 minutes before cutting, for easier serving.