How to Make It
In a large pot of boiling salted water, cook the orecchiette until al dente. Drain, reserving 1/4 cup of the cooking water.
Meanwhile, in a medium saucepan, melt the butter. Add the sliced scallions and garlic and cook over low heat until softened, about 5 minutes. Add the white wine and cook over moderate heat until reduced by half, about 5 minutes. Add 1/2 cup of water and puree the mixture in a blender until smooth. Season the scallion sauce with salt and pepper.
Wipe out the pasta pot and heat the olive oil in it. Add the arugula and Swiss chard; cook over high heat until wilted, 5 minutes. Add the pasta, scallion sauce and the reserved pasta cooking water and simmer, tossing and stirring, until the sauce is thick, about 3 minutes. Stir in the mascarpone, season the pasta with salt and pepper and serve.