Heat oil in a saucepan and saute onion until soft. Add peas and stock, bring to a simmer and cook 10 minutes uncovered. Puree the soup and season with pepper.
While the soup is cooking, make the dumplings. In a small saucepan heat the stock and semolina to a simmer. Stir and cook until thick. Remove from heat and let cool slightly. Season with salt, nutmeg and add butter.
Make dumplings with two teaspoons and add to the soup. Let gently simmer 10 minutes until dumplings float to the surface.