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