Heat olive oil in a skillet over medium-high heat. Saute onion and garlic until onion is translucent, about 5 minutes. Add prawns; cook and stir until starting to turn color, about 2 minutes. Add fish sauce and pepper; cover and cook until slightly reduced, about 2 minutes.
Pour chicken broth into the skillet with prawns. Cover, reduce heat, and simmer until flavors begin to combine, about 2 minutes. Add patola; re-cover and cook until mostly softened, about 5 minutes. Add misua noodles; let simmer until tender yet firm to the bite, about 2 minutes.