The cooking of polenta is a contentious issue that need not be explored in any great depth here. I use a Thermomix (see method here), but for the vast majority of my readers that do not have access to such an appliance, I instead refer you to this extremely comprehensive article on the best way to cook it. I suggest that you use the ingredients I have listed as they are specific to this application, but apply the recommended method.

When the polenta is cooked, spread it out thinly on a couple of baking trays (or similar), using an off-set spatula. Allow to firm up (this happens pretty quickly). Cut out rounds (or other shapes as desired) with a biscuit cutter or some other implement. Set aside.

Cut the mushrooms to your size and shape preference and sauté in a single layer in a dry pan, preheated to medium-high heat. You want to sear the mushrooms on all sides. The liquid should be exuded and evaporate pretty much as soon as it hits the pan surface - you may need to do this in batches. Set the mushrooms aside and turn the pan down to low.

Add the water and wine to the pan and scrape to deglaze. Add the garlic and stew very gently until very soft and fragrant, at least 20 minutes. If the liquid evaporates completely, the heat may be a little high, but you can just add some more water and continue cooking. Cooking the garlic slowly for this long greatly softens its bite and draws out a lot of deep flavour.

Return the mushrooms to the pan, cover and cook for a further 10 minutes (adding a little extra liquid if necessary). Stir in the crème fraîche (or vegan substitute) and herbs, then season with nutmeg, salt and pepper to taste.

Starting with mushrooms, layer sauce and polenta rounds with a little cheese on one or two of the layers if using. I used an oven-proof dish about 30cm in diameter. Use the in-between cut out pieces of polenta on the bottom layers and finish with a neat arrangement of polenta rounds on the top. Sprinkle or layer a little more cheese on top if using.

Bake uncovered in a 200c oven for about 30 minutes, until bubbling around the edges.