Cut pork into 2 x 1/4-inch-wide strips. Heat oil in a large nonstick skillet or wok over medium-high heat. Add onions, ginger, peppercorns, and chile; stir-fry 30 seconds. Add pork; stir-fry 1 minute. Add plantains; stir-fry 30 seconds. Stir in broth, soy sauce, rum, and sugar; bring to a boil. Cover, reduce heat, and simmer 15 minutes, or until plantains soften.
Combine water and cornstarch, stirring well with a whisk. Add cornstarch mixture to pork mixture, stirring well; bring to a boil. Cook 1 minute or until thick, stirring constantly.