Peel the squash then cut it in half lengthwise and use a spoon to scoop out the seeds and insides.
Dice squash into one-inch cubes.
In a large pot, melt the butter.
Add in the onion and garlic and cook until translucent.
Add the cubed butternut squash to the pot.
Pour chicken broth into the pot and bring it to a simmer.
Once the soup is simmering, cover and cook for about 20 minutes on medium heat or until squash is fork-tender.
Remove pot from heat and add cream, pumpkin pie spice, salt, and brown sugar.
Use an immersion blender to puree the soup. You can also transfer the soup to a blender to puree.
Garnish with a swirl of heavy cream before serving.