Preheat the stove to 80 degrees and heat a plate or baking tray.
Cut the lime into fine slices. Cut away the dry tips of the lemongrass and crush the stalks with the back of a knife so that the aromatic substances can develop.
Season the veal fillet with salt and season with pepper. Meanwhile, fry in the hot clarified butter all around, including the ends, for five to six minutes. At the end of the frying time, add the lime slices, lemongrass and bay leaf to the frying pan and fry briefly. Then put everything together on the preheated plate, the ingredients should be as close as possible to the meat so that it can absorb the flavors. Meanwhile, cook the veal fillet in the 80 °C stove for one and a half hours.
For the lettuce, carefully clean the leeks, cut away the root end and cut into very fine rings. Place the peppercorns in a sieve, rinse when cool and chop coarsely or pound in a mortar.
About thirty minutes before serving, heat olive oil (1) and sauté the leeks and crushed pepper in it over medium heat until the vegetables have collapsed a little. Now drizzle the lime juice, olive oil (2) and vinegar and season the salad with salt and pepper. Leave to infuse until ready to serve.
To finish, cut the veal fillet into slices as fine as possible and arrange decoratively with the leek salad.
Tip: Instead of clarified butter, you can use a frying pan in most frying pans.