Heat the vegetable oil in a large Dutch oven over medium-high heat. Add the pork cubes and brown them on all sides for about 6 minutes total.
Stir in the minced garlic and ginger. Cook for 1 minute until fragrant.
Pour in the soy sauce and chicken broth. Bring the mixture to a simmer, then lower the heat, cover, and cook for 45 minutes until the pork is tender.
Stir the cornstarch slurry into the pot and simmer uncovered for 5 minutes until the gravy thickens.
Add the bok choy and cook for 3 minutes until it softens slightly but still holds texture.
Spoon the stew over bowls of cooked white rice and top with sliced green onions.