1. Prepare the polenta following the instructions for use on the packet.
2. When cooked, spread the polenta out to form a smooth even wafer, then leave it to rest and cool for at least half a day.
3. When cold and compact, fry the polenta wafer in a pan with plenty of vegetable oil until it is crisp and golden.
4. While the polenta is still hot, lay the slices of lard on top so that the heat starts to melt them.
5. Top with the mushrooms and a sprinkling of black pepper.