Peel ginger and chop finely. Chop coriander leaves finely. Cut beef into very thin strips.
Heat oil in a wok or deep frying pan. Sear meat on all sides over high heat, stirring, until no more juice escapes. Place in a bowl. Mix lime juice, soy sauce, ground ginger and fresh ginger and add to meat, stirring to combine.
Wipe wok or pan with paper towels. Dry–roast peanuts lightly over medium heat; add to meat. Stir red onions and coriander into meat. Season with salt.
Slice pale green and white parts of spring onions on the diagonal. Cut chili in half, remove seeds. Cut into fine strips.
Spoon salad onto individual plates. Sprinkle with spring onions and chili strips. Garnish with cucumber slices and mint leaves.