How to Make It
In a large skillet, melt the butter in the olive oil over moderately high heat. Add the fennel and shallot and cook over moderate heat, stirring occasionally, until softened, about 15 minutes.
Add the radicchio to the skillet and season with salt and pepper. Cook, stirring, until wilted, about 10 minutes. Stir in the garlic and thyme and cook for 3 minutes, then add the Marsala and crème fraîche.
Meanwhile, in a large saucepan of boiling salted water, cook the ditalini until al dente. Drain, reserving 1/3 cup of the pasta water.
Stir the ditalini and the reserved pasta water into the skillet and simmer over moderately high heat until the sauce thickens slightly, about 2 minutes. Stir in the Pecorino and parsley and season with salt and pepper. Transfer to a bowl and serve hot.