Cut the radicchio into wide strips (if the radicchio is too bitter for you, you can soak it in warm water for 15-20 minutes). Peel and core the pears and cut into wedges.
Froth the butter in a non-stick pan, drizzle in the sugar and brown the pears in it over a moderate heat. Add radicchio and walnuts and fry briefly.
Cook the ravioli according to the instructions on the packet. Strain the firm ravioli, arrange on plates and pour the radicchio and walnut butter over them. Season with salt and pepper.
Also very tasty as a starter, but enough for 6 to 8 people.