In a stock pan over medium heat, melt the butter and sauté the leaks until they are soft, about 6-7 minutes.
Add the butternut squash and the sweet potato and cook, stirring, 5 more minutes.
Add the water and cook for 25 minutes, until the squash and sweet potatoes are soft.
Turn off the heat.
With an immerse blender, blend all the ingredients until creamy.
Turn off the blender and add the sage and simmer, covered, for 20 minutes.
Season with salt and pepper.
Discard the sage.
With your hands, make goat cheese pearls.
Garnish with the cheese and fresh sage sprigs.