Caramelize the powdered sugar in a pan. Add one tbsp of butter, onions and Radicchio. Cook for 2-3 minutes.
Add vinegar, thyme and grape juice and simmer until most of the juice has evaporated. Set aside and let cool.
Add the ricotta, raisins and egg and season with salt and pepper.Combine well
Bring a large pot of lightly salted water to a boil and cook the cannelloni for 8 to 10 minutes. Once cooked, place in a bowl filled with cold water. Drain well.
Preheat your oven on 400F and grease an oven dish
Fill a pastry bag with the ricotta-radicchio mixture. Fill each cannelloni and arrange them in the oven dish.
For the bechamel, heat the rest of the butter in a pan, add the flour and let brown slightly. Add the milk and broth. Cook until sauce starts to thickens. Add salt, pepper, nutmeg. Add the cheese (start with 1/2 cup but you can add more) and let it melt. The bechamel will thicken some more.
Pour the sauce over the Cannelloni and bake in the oven for 30-40 minutes. Serve with some fresh basil