Preheat your oven to 425 degrees.
Cut your squash in half and scoop out the seeds. Lay squash on a baking sheet lined with foil.
Brush 2 TBS of melted butter over the tops of your squash.
Combine brown sugar, cinnamon, nutmeg and 1/2 tsp salt in a small bowl and spread over the top of your squash.
Bake for about 1 hour until squash is tender. When done, remove from oven and set aside.
Melt additional 2 TBS of butter in a large deep pot over medium heat. Add the apple, onion and sage and season with a little salt and pepper and cook until apple and onion are soft, about 8 minutes.
When the squash is cool enough to handle, scoop the flesh out of the squash and add it to the pot with the apple and onion. Discard the skins.
Add in the chicken broth, 1 tsp salt, 1/4 tsp pepper and stir everything together. Lower the heat to medium low and then bring to a simmer, breaking up the big pieces of squash as you stir. Simmer for about 15 minutes.
Blend everything together until nice and smooth.
Return to the pot and stir in the heavy cream.
Top with additional cream and sunflower seeds when serving if desired.