Cut the foie mi-cuit into 3 layers, making sure it does not break.
Then heat a spatula in very hot water and run it over the foie mi-cuit.
Slice the black truffle with the mandolin and place the slices over the heated part of the mi-cuit.
Then put the layers of foie mi-cuit back together and wrap it in fil, pressing a little.
Leave it in the fridge for 48 hours and it is ready to taste.
Finally, serve it on a plate with some toast.