Combine 2 cups water and 2 cups chicken broth in a large saucepan.  Simmer.  Remove from heat.  Add saffron.  Pour into a measuring cup, cover, and steep for approximately 20 minutes.

Melt 3 tablespoons butter in previously used pan over med-low heat.  Add chopped onions and saute until very tender (not brown) aproximately 10 minutes.  Add cauliflower and stir to coat.  Add saffron broth.  Bring to simmer over high heat.  Reduce heat, cover, simmer until cauliflower is tender (approximately 20 minutes).

Use a hand blender to puree soup (off the heat).  Stir in half-and-half.  Simmer.  Season with salt and pepper.  (Can be made 1 day earlier--cover and refrigerate.  Gently reheat.)  Ladle into bowls and garnish with chopped chives.