Place spinach in rapid boiling salted water for 1.5 minutes. Strain.

Melt butter in a large frying pan. Add the flour and mix until it forms a light dough.

Begin adding the cream bit by bit, whisking constantly so that it doesn't get lumpy.

Squeeze all the water out of the spinach and mix into the cream.

Add salt and pepper and simmer over a low heat for 5 minutes.