Cook 2 cups orzo in salted boiling water until al dente, about 8 minutes; drain. Chop 6 scallions; cook just the white parts in a skillet with olive oil until tender, about 2 minutes. Stir in the orzo, 2 cups chicken broth, the scallion greens and a handful each of chopped parsley and dill; season with salt and pepper. Simmer until slightly thickened, about 3 minutes. Stir in 1/4 cup grated parmesan.