Preheat oven to 425 F.
Toss the prepared squash in olive oil, and place on parchment lined baking sheet.
Salt and pepper the squash generously.
Roast the squash at 425F for 30 minutes. The squash should be fork tender and slightly browning when finished.
While the squash is roasting, melt butter in a large pot.
Saute chopped onion in butter until transluscent and slightly browning, about 15 minutes.
Add roasted squash to the onion.
Add 2 cups of stock to the onion/squash mixture.
Cook for 15 minutes over medium heat, and then allow to cool to "warm" temp.
Place soup mixture into blender and blend until pureed into a smooth, creamy mixture.
Add 8 oz cream cheese and 1 tsp cayenne, salt and pepper and blend again until thoroughly mixed through.
Return to pot, and add additional cayenne, salt, or pepper if desired to taste. Keep on low heat to warm before serving.
When serving, garnish with a dollop of sour cream, chopped parsley, and a drizzle of olive oil.