In a large saute pan, melt butter over medium heat. Add oil and rice and cook for 2 minutes, stirring to coat each grain. When rice begins to make a crackling sound, add saffron threads. Add 1 cup of the warm chicken broth and cook, stirring, until the rice has absorbed the liquid. Add the remaining broth, 1 cup at a time. Continue to stir, allowing the rice to absorb each addition of broth before adding more. Test the rice for doneness, it should be al dente but creamy.