In one pan, stir fry the celery in a small portion of olive oil. When softened, add a quarter cup of sherry and cover immediately. Let simmer for 5 minutes. Add 1/4 cup chicken broth and continue to simmer.
In a separate large saucepan, stir fry the squash on medium heat until bright orange.
Pour in remaining sherry and cover immediately. Let simmer for 5-10 minutes.
Add in remaining chicken broth and add in bouillon. Add enough water so that the squash is completely covered, about 2 cups. Let cook until completely tender (you can test with a fork; if it goes completely through without resistance, it's done).
Combine butternut mixture and celery mixture into a large blender and blend until completely smooth.
Pour back into the large saucepan. Add butter, half and half, onion powder and garlic salt. When the butter is done melting in, you're done.