1. Peel and dice all vegetables. Slice chicken into thin strips.
2. Pour broth in a saucepan, add bay leaf and all vegetables except courgette. Cook for 10 minutes over low heat, then add courgette and chicken breast. Cook for 5 more minutes. Check that the vegetables are well cooked.
3. Strain vegetables from broth and set them aside.
4. Return broth to saucepan and dissolve flour in broth. Add egg white and stir. Cook for 1 minute until thickens slightly.
5. Add vegetables and stir.
6. Remove bay leaf and thyme. Purée with immersion blender until smooth and homogenous. Add broth if necessary.
7. Serve hot.
In case of severe dysphagia, it may be necessary to pass the purée through a sieve to ensure it is sufficiently fine and smooth.