Bring a large pot of generously salted water to a boil. Add the risoni pasta and cook al dente according to package instructions for about 8–9 minutes. Then drain, rinse briefly with cold water, and let cool in a bowl until lukewarm.

Meanwhile, roughly chop the walnut kernels and toast them in a non-stick pan without fat over medium heat for about 2–3 minutes until fragrant. Immediately remove from the pan and set aside.

Peel and finely chop the garlic. Wash the fresh sage leaves, pat dry, and cut into thin strips. Roughly break up the pre-cooked chestnuts with your fingers or a knife.