Add dry mushrooms to a food processor, and pulse until you get a fine powder. Add the rest of the spices and mix well. Store in a glass jar, and keep in a dry place.
Melt half the butter, and saute the leeks with salt and pepper, until they are soft and caramelized.
Remove leeks and in the same pan, add the rest of the butter, the mushrooms, and saute them with salt and black pepper, until cooked.
Return the leeks to the pan, add the quinoa, the dry mushroom mix, the fresh thyme, and 3 cups of vegetable/chicken broth or water. Bring to a boil, then reduce heat, cover, and cook until the liquid is absorbed. Add 1 more cup of liquid/broth and let it simmer until the quinoa is fully cooked.
Add the mascarpone cheese, and mix well until it fully melts. Taste and adjust seasoning.
Just before serving, drizzle with some truffle oil, and grate a good amount of Pecorino Romano cheese on top.