Place the instant polenta in a saucepan along with the boiling chicken or vegetable stock. At this point you should be working over medium to high heat. Add some extra boiling water if necessary.
Cook the polenta according to packet instructions but substitute the water in the recipe with stock. When the polenta comes away from the sides, crumble in the gorgonzola and season.
Place a pan over a medium to high heat with the olive oil. Tear the mushrooms into the pan and fry with the garlic and sage until golden brown. (This will take 5 to 10 minutes.) Remove from the pan and add the radicchio until wilted – a minute or two.
Spoon the polenta onto a large platter and top with the wilted radicchio and mushroom. Enjoy while hot.