Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain, reserving a ladleful of the pasta cooking water.
In a large skillet, heat the EVOO, 4 turns of the pan, over medium heat. Stir in the anchovies, if using, until melted. Add the garlic and cook, stirring, until lightly golden, about 3 minutes. Add the scallions and cook, stirring, for 1 minute. Stir in the Swiss chard and crushed red pepper, cover and cook until wilted, 3 minutes. Add the nutmeg and season with black pepper.
Stir the reserved pasta cooking water into the chard mixture. Add the pasta and toss.