Difficulty: Medium (2/5)
Prepare the lamb stock: Remove the fillets from the racks of lamb and crush the bones. Place the bones in a saucepan with sunflower oil, brown them, then add the washed and peeled carrot, onion, bouquet garni, garlic, and tomato. Stir well, deglaze with white wine, reduce completely, then add water to cover. Simmer for 18 minutes, strain through a sieve, degrease, and reserve.
Season the lamb fillets with salt and pepper. Heat 2 knobs of butter in a pan, sear the fillets for 1 minute per side, then finish cooking in the oven for 10 minutes. Reserve the fillets, discard the pan butter, and deglaze with the reserved lamb jus.
Drain the boxes of green and white flageolets. Sauté them separately in 2 knobs of butter each with the chopped shallots, tarragon, salt, and pepper.
