In a medium-sized saucepan, bring the broth to a simmer over medium heat. Stir in the saffron, and reduce the heat to medium low.
Heat the oil and 1 tablespoon of the butter in a heavy medium-sized saucepan over medium heat. Add the onion and garlic and stir until just tender, about 2 minutes. Add the rice, season with salt and pepper, and stir until all of the grains are well coated with the fat and onions, and the rice is turning slightly translucent, about 2 minutes.
Add the white wine, if using, and stir until it is almost completely absorbed into the rice, 1 to 2 minutes. Add 1 cup of the hot broth and simmer, stirring frequently, until the liquid is almost absorbed, about 3 minutes. Continue adding the broth 1/2 cup at a time, stirring often and simmering until the liquid is almost absorbed before adding more (you can add some water to the pot of broth if it looks like you might run low). After about 16 to 18 minutes, when the rice is still quite al dente but the dish is starting to look creamy, stir in the shrimp and another 1/2 cup of the broth and stir frequently until the shrimp are almost cooked through and the rice is al dente, 3 to 4 minutes. Add another 1/2 cup of liquid if the mixture is too thick (you want it to be quite loose).
Remove from the heat and stir in the remaining tablespoon of butter and the Parmesan. Taste and adjust the seasoning, and add a bit more broth if necessary to achieve the desired texture. Quickly ladle into a serving bowl, or individual bowls and serve immediately with the parsley and more Parmesan, if using.