Bring a large pot of salted water to a rolling boil. Add fettuccini and cook, stirring occasionally, until al dente, about 12 to 13 minutes, or your preferred doneness. Drain, reserving 1/2 cup pasta water; set aside.

Place bacon in a large skillet over medium heat and cook on both sides until brown and crisp, about 5 minutes. Remove bacon to drain on paper towels, leaving fat in skillet. Break into bite-sized pieces when cool enough to handle.

Add mushrooms to skillet with bacon fat, stirring occasionally, and sauté until lightly caramelized, about 5 minutes. Add garlic, and sauté for another 30 seconds to a minute.

Cut Brie into small cubes and add to the skillet, stirring to melt and combine. Add enough pasta water to form a smooth sauce, and stir in sun-dried tomatoes.