Melt the butter over medium heat in a large skillet with a tight-fitting lid. Add the spaghetti and toast until deep golden in color and very nutty-smelling. Add the rice and stir for a minute. Season with some salt and pepper, add 3 1/2 cups of the stock and bring to a low boil. Reduce the heat to low, cover and cook until the rice is just tender, about 18 minutes; add extra stock as necessary if the pan gets too dry. Fluff the pilaf with a fork. Mix in the currants, pignoli, chives and parsley.