Heat the oil in a large saucepan placed over a high heat. Season the veal fillet with salt and pepper and fry until brown all over. Remove the veal from the pan and set aside. Reduce the heat, add the wine and deglaze the pan.
Return the veal to the pan, add the butter and stock, garlic, thyme and bay leaves. Simmer gently for 30 minutes. When the cooking time us up, turn off the heat and allow the fillet to rest in the stock for 20 minutes.
Meanwhile, to make the lentils, heat the oil in a large saucepan placed over a medium heat. Add the shallots and garlic and cook for 2–3 minutes. Add the carrot and celery and cook for a further 2–3 minutes.
Add the lentils with enough of the cooking liquid from the veal to cover the lentils. Cook for 15–20 minutes, or until the lentils are tender and all the liquid has absorbed. Stir in the chopped herbs.
Meanwhile, fill a deep-fat fryer or a large, deep, heavy-bottomed pan two-thirds full with the oil. Heat to 180C (a cube of bread should turn brown in one minute when dropped in.) CAUTION: Hot oil can be dangerous. Do not leave unattended.
Sprinkle the onion with salt, put in a colander over a bowl and leave to drain. Squeeze the onions in a clean tea towel and toss in seasoned flour. Deep-fry for 2–3 minutes until golden-brown. Drain on kitchen paper.
To serve, thinly slice the veal. Spoon the lentils into a serving dish, arrange the veal slices on top and scatter over the crispy onions.