Bring large pot of water to a boil.
Preheat oven to 200ºF. Place a large shallow serving bowl in oven to warm.
In a small pot, combine saffron threads and stock and bring to a boil. Reduce heat to low and let the saffron steep.
When water boils, season with salt and add pasta and cook to al dente.
When pasta is just about done, remove dish from the warm oven and scatter butter pats into it, place drained pasta over top. Pour saffron liquid over pasta and scatter in half of the cheese, toss 1 minute. Then add more cheese and continue to toss another 1-2 minutes until the pasta is evenly coated and cheese has melted into saffron broth to form a creamy, lightly golden sauce. Serve immediately.