Preheat oven to 400F, and line baking sheet with aluminum foil.
Slice spaghetti squash in half, lengthwise, and bake for one hour.
Steam broccoli. I like to do this in the microwave for ease: place broccoli in microwave-safe bowl, add two tablespoons of water, cover with microwave-safe plate, and microwave on high for 3-4 minutes, or until broccoli is softened to your liking.
Combine all cheese sauce ingredients in blender or mixing bowl, and mix thoroughly.
When spaghetti squash is done, remove the seeds, and use a fork to scrape out the "noodles" into large mixing bowl.