Remove the outer leaves of the lemongrass stalks and then remove the roots, around 1cm from the base. Slice the soft parts of the stalk thinly. Knot what remains of the lemongrass stalk and then set them aside.
Place the beef strips in a wok or large saucepan over high heat. Pour in the water and add the knotted lemongrass stalk and oyster sauce. Mix well. Bring it to a boil and then reduce the heat to low. Let it simmer for 6-8 minutes or until the liquid evaporates and becomes soft.
Add more water if needed. Once the beef is cooked, allow it to cook in its own oil for 2-3 minutes or until the edges are brown. Transfer the beef to a plate.
Put the oil in the wok which you used to fry the beef and then set the heat to medium. Fry the garlic, onions, chili and lemongrass in the wok for 2-3 minutes or until they are fragrant and the onions are translucent. Add the asparagus and stir fry it for another 3 minutes until they are bright green and soft enough to eat.
Return the beef to the wok with the stir-fried asparagus. Include the juices on the plate.
Add the soy sauce and stir-fry the beef and vegetables for another 4 minutes or until warm. Season it with salt and pepper.
Transfer the stir-fried lemongrass beef to a serving plate and garnish it sprinkle it with chili. Garnish it with coriander before serving. Serve warm with steamed rice.