If using fresh beans, bring a medium pot of water to a boil over high heat, add beans, and cook until tender, about 20 minutes. Drain and set aside in a bowl of ice water. If using dried beans, drain soaking liquid, put beans in a medium pot, cover with cold water, and bring to a boil over medium-high heat. Cook until tender, about 50 minutes, drain, and set aside in a bowl of ice water.
Cook peas in a small pot of salted water over medium heat until just tender, about 10 minutes. Drain and add to beans.
Meanwhile, heat oil in a large skillet over medium heat, add scallions, and cook until soft, about 5 minutes. Increase heat to medium-high, add scampi, season to taste with salt, and cook, stirring constantly, until scampi turn opaque, 1–2 minutes. Remove skillet from heat. Drain beans and peas, then add to skillet.
Cook fusilli in a large pot of boiling salted water over high heat until just tender, about 7 minutes. Drain and add to skillet. Cook over medium heat, stirring to mix ingredients well, for 1–2 minutes. Just before serving, season generously with salt and pepper.