Cream of spinach soup recipe?
You know this. Sautee onions in butter. Add fresh spinach and wilt down, or add thawed frozen spinach with its liquid as well. Add stock or water. Cook a bit. Blitz in blender or use a stick blender. Then add cream, half and half, whatever you have.
My only suggestion would be to add grated nutmeg somewhere along the line. Not too much, maybe 1/4 t for 4 to 5 cups of soup?