1. In a medium saucepan, combine the chicken stock with the asparagus ends and mint sprigs and bring to a boil. Reduce the heat to low, cover and keep hot.
2. In a large saucepan, toast the fennel seeds over high heat, stirring a few times, until fragrant, about 1 minute. Transfer the seeds to a mortar and let cool completely. Coarsely grind the seeds with a pestle.
3. In the same saucepan, heat the olive oil. Add the onion and celery and cook over moderate heat until softened, about 5 minutes. Add the rice and ground fennel and cook, stirring to coat the rice with oil. Add the wine and cook, stirring, until absorbed, about 2 minutes.
4. Add enough hot stock to just cover the rice and cook, stirring constantly, until the stock has been absorbed. Continue adding stock 1 cup at a time and cook, stirring constantly, until the rice is just tender, about 20 minutes total. Stir in the sliced asparagus and cook, adding more broth as necessary, until the asparagus is crisp-tender and the rice is al dente and bound in a creamy sauce, about 5 minutes longer.
5. Stir the butter into the risotto. Stir in the cheese and the chopped mint and season with salt and pepper. Spoon the risotto into bowls and serve, passing more cheese at the table.
Recipe by Andy Glover via Food & Wine Magazine