Heat half the oil in a large wok or non-stick frying pan over a high heat. Cook half the beef for 1-2 minutes, or until browned, breaking it up as it cooks. Set aside in a large bowl. Repeat with remaining oil and beef. Cool slightly.
Add remaining ingredients to beef and toss to coat. Serve with cos leaves, rice, prawn crackers and lime wedges.
Beef stir-fry strips would also work well in this recipe.
You can adjust the flavours (hot, sour, salty and sweet) to taste, by using more or less chilli, lime juice, fish sauce and sugar.
Add some wedges of cucumber and thinly sliced snow peas, if desired.