Difficulty: [usr 2]
Peel and wash the carrots, turnips, and leeks. Place them in a large saucepan with the chuck and all the spices (star anise, cinnamon stick, and saffron). Add about 1.5 liters of water, bring to a boil, then reduce to a simmer for 1 hour. Meanwhile, peel the potatoes.
Strain the broth, return it to a low simmer with the orange and lemon peels, then add the potatoes to cook for about 15 minutes until tender.
Cut the beef tenderloin into four even slices. Tie each with kitchen twine to hold its rounded shape, leaving a long piece of string attached to each.
Ten minutes before serving, poach the beef slices for 5 minutes in the simmering broth: suspend them by the strings from a wooden spoon laid across the pan so they don't touch the bottom. Drain and keep warm.
Return the vegetables to the broth for a few minutes to heat through. Arrange the four beef fillets in preheated soup plates, add the vegetables, ladle over a little spiced broth, and finish with a sprinkle of Guérande salt just before serving.
Serve piping hot.
