Steam fresh spinach or cook frozen. (See VITAMIX INSTRUCTIONS BELOW)
Put spinach in pan with no more water than necessary with salt.Cook for a few minutes, just until wilted.
Allow to thoroughly cool, and squeeze water using paper towels.I wrapped steamed spinach in paper towels and refrigerated overnight.
Put onion in cold pan with butter. Saute until soft. Add spinach and cook for 2 -3 minutes.
Add broth, milk and a small grating of nutmeg. Bring to a simmer and stir from time to time.
Cook about 20 minutes. Add cheese.
Add to Vitamix and mix just enough to still have some heft of the spinach.
Stir, cook until cheese integrated. Season with salt to taste.
Serve at table with crostini, more cheese and optional olive oil to top off.