Melt the butter with a little oil in a saucepan and fry the onion and garlic until the onion is soft and translucent.
Add the carrots, celery, leek and bay leaf – sprinkle over the herbs and season with salt and freshly ground pepper. Let it heat through for a moment.
Stir in the flour and cook it through for a minute or so, then add the orzo and stock. Let it simmer until the orzo is half cooked.
Add the chicken and cream and let the soup simmer until the orzo is tender and the chicken is hot.
Season the soup with freshly squeezed lemon juice and, if you like, a little lemon zest – plus salt and freshly ground pepper – and finally stir in the parsley.
Serve the soup with a few fresh lemon slices for a pretty finish, if you like.