Melt butter in a pan, add the onion and fry gently for 5 minutes with out browning.
Add the flour and cook a further 2 minutes, stirring all the time. Remove from the heat and gradually add the milk, beating vigorously after each addition.
Return to the heat and bring to the boil stirring constantly.
Lower the heat and simmer 2 minutes stirring occasionally, then stir in the cream, herbs, and salt and pepper to taste. Fold in beetroot and apple and simmer a further 5 minutes, stirring occasionally.
Remove from heat and leave to cool, stirring occasionally to prevent skin forming.