Combine eggs, ground pork, sliced button mushrooms, chopped scallions, fish sauce, and sugar in a mixing bowl. Thoroughly mix all the ingredients until well incorporated.
In a non-stick pan or saucepan, heat a tablespoon of cooking oil over medium-high heat.
Once the oil is hot, pour the egg mixture into the pan, spreading it evenly using a spatula.
Allow the omelette to cook for approximately 2-3 minutes until the bottom turns golden brown.
Gently flip the omelette using a spatula and continue cooking until the other side is also golden brown and the egg is fully cooked.
Serve the omelette hot alongside rice or other side dishes, completing your traditional Vietnamese meal.