Heat a dry frying pan over a medium flame. Remove from the flame and put in the saffron. Let the residual heat from the frying pan toast the saffron, then crush to a powder with a wooden spoon or in a pestle and mortar.
Transfer to a small bowl, cover with a little water, and leave to soak.
Peel and slice the carrots into rounds. Peel and dice the apples. Peel and mince the ginger. Grate the lemon zest and press the juice. Put the carrots, apples, ginger, bay leaves, soaked saffron, and water with a little salt together in a soup pot.
Cover with a lid, bring to a gentle boil over a medium flame, turn the flame low and simmer for 15-20 minutes or until the carrots are very tender.
Remove the bay leaves. Stir in the lemon juice and zest and transfer to to a blender. Blend until perfectly smooth in a food processor, or with an immersion blender. Then season to taste with salt and white pepper. Just before serving, stir in the soya cream.