Coat beef in the garlic, salt, and pepper. Set aside for half an hour.
Soak noodles in boiling water (follow instructions on pack). While this is happening add the peanut oil to a wok on high and heat until smoking, then add the beef and quickly brown it. Add the chillies, fish sauce and sugar, and stir fry.
Remove from heat and stir in fresh coriander. Serve over noodles.
