Bring the stock or water to the boil and reduce to a low simmer. Ladle a little of it into a small bowl. Add the saffron strands and leave to infuse.
Heat the oil in a large saucepan. Add the onion and garlic and cook gently for about 5 minutes until softened. Add the pumpkin and rice and cook for a few more minutes until the rice looks transparent. Pour in the wine ans allow it to bubble hard. When it is absorbed add a quarter of the hot stock or water and the infused saffron liquid. Stir until all the liquid has been absorbed.
Gradually add the stock or water, a ladleful at a time, allowing the rice to absorb the liquid before adding more, and stirring all the time. After 20-30 minutes, the rice should be golden yellow, creamy and al dente.
Stir in the Parmesan cheese, cover the pan and leave the risotto to stand for 5 minutes.
To finish, stir in the pistachios and marjoram or oregano. Season to taste with a little salt, nutmeg and pepper, and scatter over a few marjoram or oregano leaves.