Heat 1 tablespoon of olive oil in a skillet on medium-high heat. Add the onion once the oil is hot, and sauté for 5 minutes. Add the mushrooms, garlic, Italian seasoning, and salt & pepper, then cook for another 5 minutes, stirring occasionally, until everything has softened, and the liquid is released from the mushrooms.
Meanwhile, set your oven's broiler to high and move the rack to the top third of the oven.
Place the naans on a non-stick baking sheet. Drizzle a teaspoon of olive oil onto each naan. Top each naan with the mushrooms followed by the cheese.
Broil for 5-6 minutes, or until the cheese is melted and bubbly. Drizzle the truffle oil on top of each pizza, and sprinkle with parsley. Serve immediately.
If you can't find Fontina cheese, you could try substituting Gruyère, Provolone, or Gouda.