Get a large pot of salted water on the stove and bring it to a boil. Boil the potatoes until they are fork tender and mashable, about 20 minutes.

While that happens, get a large rondeau pan on the stove and heat the truffle infused olive oil over medium high heat. Add all of the mushrooms in and let them get brown and cooked down for about 5 minutes. Season them with salt and crushed red pepper. Add in the onion and garlic and let them get fragrant for about 2 minutes. Then take the mixture off the heat and set it aside.

In a small pot, gently melt the stick of butter over medium low heat. Pour the milk in with it along with the nutmeg and stir it together. Let it get hot and gently simmer without letting it boil.

The potatoes should be done by this point, drain them and return them to the pot they boiled in. Pour the hot milk mixture over them, and add in the parmesan cheese. Stir it all together until it is a smooth, thick liquid.

Pour all of the mushrooms into the creamy liquid and stir them in. It will almost be like a thick cream of mushroom soup. Pre-heat the oven to 375 degrees. Transfer the creamy mushroom mixture into a 9 x 13 baking dish and smooth it out, then top it off with the breadcrumbs.

Bake the wild mushroom gratin for 25 minutes, until it is thick and bubbly and the breadcrumbs are golden. Take it out and let it cool for 5 minutes. Then just scoop it out onto plates and serve! This is a perfect side dish for any meal.