I first made this soup with Acorn squash.  Schneider is right, it was too bland.  Use the Butternut. (Couldn't find a Buttercup variety.) 
 
 

Chef's Privilege:  I hold strongly to the view that the predominant flavor of a soup (and other foods as well) should be that of the main product.  A squash soup should taste of squash; a tomatillo soup should taste like tomatillos.  Don't make the stuff and then load it with seasonings that, in effect—if not design, mask rather than enhance the taste.  If you don't like the taste of squash, pass it by.  Your guests are far more likely to appreciate the taste-hints within your squash soup than be overwhelmed with brown sugar, cognac or whatever else you've added "creatively." I came to this life-changing revelation in 1958 when my brother gave me a copy of The Fine Art of Mixing Drinks, by David Embury (out of print, but still available), which was already a classic ten years after its publication.  Embury’s basic principle of drink mixing is that a gin martini should taste like gin not vermouth; a margarita should taste of tequila not lime juice, and a bourbon highball (remember those) should taste like bourbon—preferably sour mash bourbon.  (Vodka??  Well, you will have to read the book.)

So here we have squash soup that tastes like squash.  To be more sure of that, I add a sachet of squash seeds and fiber, from the center of the raw squash, as a flavor enhancer.  This soup is “polished” with a little heavy cream just before serving.  I tried it with and without cream and with and without a splash of cognac.  A little cream, just enough to lighten the color a bit and smooth the taste of squash, is nice. Forget the cognac.

BUTTERNUT SQUASH SOUP
Yield:  about six servings
See Abbreviations if needed
·   3         butternut squash, medium size
·   2T       extra virgin olive oil (EVOO)
·   2         large shallots, diced
·   5 C     chicken stock or canned broth
·   ¼ t      fresh grated cinnamon 
·   1         sachet or cheese cloth pouch of squash fiber and seeds
·   1         sachet of a dozen parsley stems and a dozen black pepper corns
·   salt      to taste (it will need 2 teaspoons or more)
·   1T       brown sugar, to taste, but not much 
·   2 oz     heavy cream, or less
·   6         croutons per serving, seasoned as desired

1.  To prepare the squash: 
     ·  cut the squashes lengthwise with a large, sharp chef's knife or cleaver
     ·  remove the seeds and fiber and reserve
     ·  place the squash halves in a sheet pan and fill it with 1/3 inch of water
     ·  bake in the oven at 350F for about 35 minutes or until tender
     ·  let cool, scoop out the flesh and set aside 
2.  In a soup pot, sweat the diced shallots in EVOO to soft and translucent
3.  Add a cup of stock, the cinnamon, some salt and the two sachets
4.  Add the squash, the rest of the stock and stir thoroughly
5.  Bring to boil and simmer for about 5 minutes
6.  Remove the sachets and set aside
7.  Puree the soup in the pot with a stick blender, 
     or in a countertop blender, in batches
8.  Return the sachets to the pureed soup and simmer for about 20 minutes
9.  Remove the sachets and discard
10.  Taste the soup and adjust the seasoning
     ·  If there is a too strong hint of bitterness, add some brown sugar
     ·  Assess the need for more salt
11  At service, a la minute:
     ·  return the soup to boil and then remove from heat
     ·  add one ounce of heavy cream.  Stir in.  Look and taste
     ·  add  a second ounce, maybe . . 
     ·  serve hot in heated bowls immediately
12. Garnish with croutons or a dollop of creme fraiche