Bring a large pot of salted water to a boil. Add the spaghetti and cook as the label directs.

Meanwhile, heat a large skillet over medium-low heat and add 2 tablespoons olive oil. Scatter the leeks in the skillet and season with 1 teaspoon each salt and sugar. Cook, stirring occasionally, until tender, about 10 minutes.

Drain the pasta, reserving about 1 cup of the cooking liquid. Add the pasta and the reserved cooking liquid to the skillet with the leeks. Add the remaining 2 tablespoons oil, 1 teaspoon sugar and the balsamic vinegar. Increase the heat to medium-high and add the radicchio and cheese. Toss until the cheese melts, 3 to 5 minutes. Season with salt and top with the hazelnuts.

Per serving: Calories 692; Fat 34 g (Saturated 11 g); Cholesterol 49 mg;

Sodium 966 mg; Carbohydrate 78 g; Fiber 13 g; Protein 26 g

Photograph by Antonis Achilleos