Heat a large pan or wok over medium high heat. Add 2 tablespoons of oil. Add half of the noodles to the oil, stirring well to coat the noodles in oil. Add the sweet soy sauce. Add a little cold water, if the noodles get too sticky. Fry for a minute or two, until the noodles are soft and coated in sauce. Remove noodles and set aside.
Repeat with the remaining noodles, oil and sweet soy sauce. Add to the other noodles and set aside.
Heat the 2 remaining tablespoons of oil in the same pan. Add the onions and fry until softened. Add the garlic and preserved radish and fry until lightly brown. Add the curry powder, fry to release aroma, then add the beef. Fry until the beef is cooked through.
Add the stock and peas. Let come to a soft boil. Add the cornstarch mix. Stir well to mix in. Let come to another boil and simmer gently for a few minutes. Taste and add fish sauce or sugar, if needed.
Serve spooned over the noodles and garnished with a sprinkle each of scallions and cilantro.