1. Put the dried mushrooms in a heatproof bowl and cover with boiling water. Let stand for 20 minutes. Line a fine sieve with moistened cheesecloth or paper towels. Strain the mushrooms through the sieve, reserving the liquid. Rinse the mushrooms.

2. Meanwhile, heat the oil in a large frying pan over medium heat. Add the garlic and cook, stirring, for 2–3 minutes until golden. Stir in the cremini mushrooms and thyme, and season with salt and pepper. Add the porcini mushrooms and their soaking liquid, the rosemary, and the sage, and cook, stirring occasionally, until the mushrooms are lightly browned and the liquid has almost completely evaporated.

3. Bring 4 cups water and salt to a boil in a large saucepan over a high heat. Slowly whisk in the polenta. Whisk about 3 minutes more, until the polenta is thick and tender. Season with salt and pepper.

4. Divide the polenta between 4 serving bowls. Spoon the mushrooms on top and serve at once.

Variation: Parmesan Polenta

Omit the mushrooms. When the polenta is tender, stir in 6 tbsp diced butter and ¾ cup freshly grated Parmesan cheese.