Coat butternut squash with olive oil and salt and pepper.
Roast on a medium baking sheet for 15-20 minutes or until just fork-tender.
Preheat oven to 350.
Bring a large pot of heavily salted water to a boil and add broken lasagna noodles. Boil for 1-1.5 minutes under al dente. Drain (saving 3/4 cups of pasta water) and set aside.
In a medium-large cast iron skillet, melt butter over medium heat. Once bubbly, add garlic and cook until fragrant. Add cornstarch and whisk to create a paste, cook 2 minutes. In two batches, slowly add the milk while whisking to avoid lumps.
Add cheeses to bechamel (milk and cornstarch) and whisk until smooth. Stir in herbs, spices and kale. Gently (in batches, if necessary) stir in lasagna noodles and roasted squash to coat in sauce.
Pour reserved pasta water around edges of cast iron skillet. Arrange prosciutto on top of pasta and place in oven for 25-30 minutes. Watching carefully to make sure prosciutto doesn't burn.