In a Dutch oven or heavy pot over medium heat, saute onions and garlic in 2 tablespoons of cooking oil.
Add the cubed pork belly, a pinch of salt and pepper. Cook until it turns slightly brown. Stir occasionally to cook evenly.
Pour the vegetable broth and fish sauce. – Add the elbow macaroni to the Dutch oven and cook until it turns al dente.
Add the shredded cabbage, sliced carrots, and celery.
Pour the evaporated milk, and stir to combine. Taste and adjust the seasoning with salt and pepper. Turn off the heat.
To serve, ladle soup in individual bowls.