You begin with a simple soffritto of onion in butter and olive oil, into which you add the chopped radicchio (preferably radicchio rosso di Treviso—see Notes below), seasoning with salt and pepper and turning to let the radicchio absorb the flavor of the onion over moderate heat. When the radicchio is well wilted (and it will turn color to a kind of burnt sienna) then adding a splash of red wine and allow it to evaporate, then add water or broth, enough to wet all the ingredients well without covering them. Cover and allow to braise about 15 minutes or longer, until the radicchio is tender and the liquid well reduced. (Some recipes call for a simmering time as long as 45 minutes.)

While the radiccchio is braising, make the béchamel sauce. Add the heavy cream and grated parmesan cheese and, when done, the radicchio and its braising liquid. Mix well.

Cook your pappardelle in abundant salted water and, when they are still a quite underdone, add them to the béchamel, cheese and radicchio mixture. The mixture should be quite soupy—remembering that the sauce will simmer and reduce and get absorbed by the pasta during the next step.

Pour the mixture into a oven-proof casserole or gratin dish, top with more grated parmesan cheese, and bake in a very hot oven (230C/450F) for about 20 minutes, or until it is lightly browned on top. Allow to cool off for 5 minutes or so before serving.