Can be made
up to two days ahead and gently
reheated until piping hot.
Heat the butter in a saucepan,
then add the onion and cook for
5 mins until softened. Stir in the
flour and cook for 2 mins, then
slowly start to whisk in the milk.
When it has all been incorporated,
gently cook for 5 mins until the
sauce has thickened.
Meanwhile, place the spinach in
a large colander. Pour over a kettle
full of boiling water until the leaves
have wilted (you may have to do
this twice). Place the spinach in a
clean dishcloth, squeeze out any
excess liquid, then roughly chop.
Stir into the sauce with the cream,
gently heat, then finely grate over
some nutmeg and season well.