Put the butter, oil and onion in a saute pan large enough to accommodate all the radicchio and endive (it's fine if it forms a heaping mound) over medium heat. Cook until the onion has turned a rich golden color.
Add the bacon and continue cooking until it becomes lightly browned but not crisp. Add the radicchio and endive, season with salt and pepper and stir until the vegetables are coated with the oil and butter. Lower the heat to low, cover the pan and cook, stirring occasionally, until the endive and radicchio has wilted completely and achieved an almost creamy consistency, about 15-20 minutes.
Bring 4 quarts of water to a boil.
Uncover the saute pan, raise the heat to medium high and let any liquid the vegetables have given off boil away. Add the cream and cook until it has reduced by half. Stir in the parsely and remove from the heat.
Add 1 Tb. salt to the boiling water, drop the Fettuccine and stir. When they are cooked al dente drain well, return the sauce to a low heat and toss the pasta in it with the parmesan cheese. Serve at once.
From: Giuliano Hazan
The Classic Pasta Cookbook
1993, London and New York, Dorling Kindersley
Used with permission