Preheat the oven to 180 °C top/bottom heat. Coarsely chop the walnut kernels, spread them on a baking sheet, and roast in the oven for about 5 to 7 minutes until golden brown and fragrant. Then set aside.

Wash the radicchio, pat dry, cut out the core, and slice the leaves into strips. Peel and finely dice the shallots and garlic. Finely grate the Grana Padano.

Bring a large pot of salted water to a boil and cook the tagliatelle until al dente. Before draining, scoop out about 100 ml of pasta water and set aside.