Bake the squash until done.
In large pot melt butter add potatoes and onion.
Cook until onion is translucent.
Add minced garlic
Cook a minute or two.
Add chicken broth, rosemary, and salt...simmer about 20 minutes
Add cooked squash, cover and bring back to boil. Remove from heat.
Use an immersion blender and blend until smooth.
Stir in 1/2 and 1/2.