Preheat oven to 350°. Lightly grease casserole dish with non stick spray.

Prepare squash noodles: Peel, halve and seed the squash. Cut off the lower third of the squash (the part where the seeds have been removed) and reserve for another use. Slice the neck of the squash into long strips that resemble wide lasagna noodles, about 1/8 inch thick. It is helpful to use a mandoline, but a long slicing knife will also work. (I cut mine into small slices to make it easier to handle, they tend to break apart if boiled too long)

Bring a large pot of salted water to a boil. Cook the squash noodles until they are slightly tender, 4-5 minutes, then gently remove the noodles with a slotted spoon.

Prepare the spinach: Heat 1 tablespoon of the olive oil in a large saute pan. Add onions and cook till translucent, 4-5 minutes. (I used season blend, which is a bag of chopped onions, red bell peppers & celery already chopped.) Add garlic and cook till fragrant, 1 minute more. Add the spinach in batches, allowing it to cook down before adding more. Cook until all spinach is wilted, 5-6 minutes. (I only used about 3 cups of spinach)

In a medium bowl, mix ricotta with nutmeg and sage. (I didn't have nutmeg so I used 1/4 tsp ginger instead)

Cover the bottom of the prepared dish with a layer of squash. Top with a third of the ricotta any gently spread it evenly.

Drizzle with 1 tablespoon of olive oil and sprinkle with salt and pepper. Top with half the spinach mixture.

Continue layering, and finish with a layer of squash, ricotta and a final drizzle of olive oil. Top with the mozzarella cheese.

Bake until filling is bubbly and the mozzarella is golden brown, 35-40 minutes Let cool slightly before serving to let the layers set.