Cut lettuce into small portions. In a large pot of water, add pinch of salt and 1/4 teaspoon of vegetable cooking oil. Then blanch the lettuce for 10 seconds. Transfer out and placing in serving plate.
Mix 1 teaspoon of cornstarch with 1 tablespoon of water. Set aside.
Add 1 tablespoon of vegetable cooking oil in wok, and fry garlic until aromatic. Then add oyster sauce, sugar, light soy sauce. Then add around 1 cup of water in. Simmer for 1 minute and then pour in the cornstarch water. Mix well.
Pour the sauce over blanched lettuce and serve hot.