Cream of Spinach soup

As seems to happen with me every few months, once again I'm mildly aneamic. Instead of resorting to iron pills which don't agree with me all that well I'm taking a more natural route - starting off yesterday evening with some homemade spinach soup - absolutely delicious even if I do say so myself. Here's the recipe which is a mixture of stuff I've seen online and a bit of my own inspiration (I measured out amounts pretty much guessing as I went along, but if you taste as I go I think it's quite hard to go wrong with this one).

Ingredients (will serve 4 'normal' people or 2-3 greedy guts like us):
1 huge bunch of spinach (stalks trimmed)
Good vegetable stock (I used Aneto - all natural, no additives) - around a third of a litre.
Around 1/4 litre of milk
A largish onion finely chopped
Big chunk of butter
Flour a desertspoon or a bit more
2 slices of cured sheep's cheese - though given the choice I would have used a Kraft cheese slice here (something that is normally inedible but comes into its own when used in green vegetable soups)
Cream - a good dash and extra to serve
White pepper
Salt

In a big pot melt the butter and add the onion, fry gently until transparent. Sprinkle flour over the top and blend in to make a thick paste/roux type mixture. Gradually blend in the milk- when dissolved add the stock and bring to the boil - I've been pretty inexact about the quantities of stock and milk but basically they should be 50:50 an reach up to about 2.5 inches above the base of the pot. Add the spinach and cook on a medium heat until wilted and soft. Remove from the heat and blend with a hand blender until smooth. Crumble the cheese into the soup and whizz with blender. Whizz in a little flour if it's too runny. Check seasoning, adding white pepper and salt. Serve with a swish of cream and crusty bread. Enjoy!