Heat vegetable oil in a small saucepan. Add ground pork and minced garlic. Sauté till pork turns opaque, about 1 minute.
Pour in water and bring it to a boil. Reduce heat to low. Season soup with ground pepper.
Crack salted egg into a bowl. Gently pour it into the soup. Allow soup to simmer gently for 5 minutes to cook egg yolk. Taste soup and add a little salt if necessary.
Add lettuce leaves and cook for another minute. Turn off heat. Pour into a bowl. Drizzle sesame oil on the top.
Serve immediately with dried rice cake or a bowl of steamed rice and toasted seaweed.