White truffle oil is a wonderful but assertive flavor, and a little goes a long way. If you're unsure of how much truffle flavor you prefer, start with 1 teaspoon and add more to your own taste. Slideshow: Mushroom Recipes
Bring the vegetable stock and water to a simmer in a medium saucepan.
In a large saucepan, melt one tablespoon of butter and one tablespoon of oil over moderate heat. Add the mushrooms and thyme, and sauté until the mushrooms are browned and tender, about 5 minutes. Remove from the pan and set aside. In the same pan, sauté the onion and garlic over moderate heat until softened, about 5 minutes. Add the millet and cook, stirring, for 2 minutes. Add the wine and cook 1 minute.
Add the stock mixture to the millet 1 cup at a time, stirring occasionally, and adding more stock once it has been absorbed, about 30 minutes total. Once the millet is al dente, remove from the heat and add the butter, truffle oil, and cheese. Season with salt and pepper and serve.
The mushrooms can be sautéed a day ahead. Store in an air-tight container and refrigerate.
If eating a gluten-free diet, be sure to use gluten-free stock.