Reduce the mi-cuit foie gras to a purée, then set aside in a cool place.
Chop the truffle, sweat it in a saucepan with 20 g of butter for 2/3 minutes over a gentle heat.
Use the alcohol to de-glaze the pan. Reduce until nearly dry.
Moisten with the truffle juice and veal stock. Season with salt and pepper.
Cook for 5 minutes, then beat in 20 g of butter and the foie gras purée. Keep warm.
Peel the celery and cut into thin batons, then sauté briskly with the remaining butter. Keep warm.
Cook the foie gras escalopes on a plancha or flat griddle for 2/3 minutes each side. Finish cooking in the oven, if necessary.
Griddle the tuna steaks in the same way. Roast them until pink.
Season the foie gras and tuna with the flower of salt and coarsely ground pepper.
Arrange the celery on the plate, with the tuna on top, followed by the foie gras escalope.
Decorate with a few tatsoi and lovage leaves.
Drizzle with a little truffle sauce.
