Finely chop a large shallot, put it in a sauté pan with the white wine, bay leaf and thyme, reduce gently by half, add the veal jus and the liquid cream, reduce until the juice has a coating consistency , out of the fire add the strong mustard (4 tbsp), strain, and add the Meaux mustard (2 tbsp), check the seasoning, set aside.
Cut onion rings, blanch quickly, fry in oil, set aside.
Trim the fat from the kidney, split it in half lengthwise to eliminate the white parts, cut it crosswise into thick strips, salt, pepper, brown the slices for 2 minutes in a pan with very hot oil on each side , put in a colander and let the kidney drain.
Warm up the lentil puree, arrange in two dumplings, in a circle under the dumplings arrange the slices of kidney, heat the sauce and add a few mustard seeds, whisk in butter, coat the kidney and surround with a cord of sauce, add a few fried onions, a few diced tomatoes and chopped chives.
Prepare the mash:
Sort and wash the lentils, cover them generously with cold water in a large container, bring to the boil and skim, add coarse salt and pepper, 1 bouquet garni, a large onion studded with two cloves and a carrot cut into diced, a few mahaleb seeds, cook covered and gently simmer, remove the bouquet and the studded onion, pass the hot lentils through a vegetable mill, heat the purée gently, working it with a wooden spoon and thicken it with butter fees.
