In a bowl, combine the ground pork with mirin, soy sauce, minced ginger, and minced garlic. Mix well and let it marinate for 15 minutes.
Heat the vegetable oil in a large saucepan over medium-high heat. Add the marinated pork and cook, stirring frequently, until browned and cooked through, about 5-7 minutes.
In the saucepan with the cooked pork, add the chicken broth and evaporated milk. Stir to mix, then bring to a gentle simmer over medium heat.