Bring broth to a boil in a large pot with a tight-fitting lid. Meanwhile, toast quinoa in a large, dry saute pan over medium-high heat, stirring constantly. When quinoa turns golden in spots and starts to smell toasted and nutty, about 5 minutes, remove from heat. Pour quinoa into boiling broth, reduce heat to a simmer. Cover and allow to simmer for 15 minutes. Remove from heat and allow to rest, covered, for 5 minutes more. Fluff with a fork and add scallions, stirring to combine.