1. Start by cleaning your mushrooms if needed with a dry towel or brush, then chop them in slices.
2. Heat up some oil in a pan, crush the garlic cloves and add them to the pan. Fry for a couple of minutes. Add the mushrooms and the thyme and fry for a few more minutes, until golden-brown. Turn off the heat and add the truffle oil, salt and black pepper. Keep warm.
3. Bring the stock to a boil in a pot, then slowly stir in the polenta. Reduce the heat to the minimum and cook stirring constantly.
4. When the polenta is done (around 30 minutes or according to package) stir in the parmigiano, previously grated, and the butter.
5. Spread the polenta on a board or platter, and top it with grated hard cheese of your liking, the mushrooms and their cooking juices.