Instructions:

1. Heat the vegetable broth and keep it warm.
   
2. Meanwhile, peel and finely chop the onion.
   
3. In a deep pan, melt a little butter over low heat. Add the onion and sauté, stirring frequently, until it becomes translucent.
   
4. Meanwhile, clean and finely slice the radicchio into thin strips.
   
5. Add the rice to the pan and toast it, stirring continuously, until the grains start to turn slightly translucent.
   
6. Pour in the red wine and let it cook over high heat until the alcohol evaporates (the strong wine aroma will fade).
   
7. Add the radicchio to the pan along with a couple of ladles of broth. Stir well. Continue cooking over medium heat, stirring occasionally and adding more broth as needed to maintain a creamy consistency.
   
8. While the risotto is cooking, cut the Gorgonzola into pieces and chop the walnuts.
   
9. Once the rice is cooked, remove the pan from the heat. Add the Gorgonzola and stir until fully melted and incorporated.
   
10. Serve the risotto topped with chopped walnuts and a sprinkle of black pepper to taste.