A wholesome, deeply comforting soup crafted from slow-simmered stock, aromatic garden vegetables, and fresh herbs, served with crusty bread.
Cook the onion, carrot, and celery in the olive oil for 5 minutes.
Add the potato and 1.5 litres of water, then simmer for 15 minutes.
Add the fish fillets and simmer for 8 minutes until flaking, then break into bite-size chunks.
Whisk the lemon juice with the egg yolk, temper with a ladle of hot broth, and stir back into the pot.
Warm through without boiling, season with salt, and serve hot.