Steamed Pacific Oysters with Mirin and Soy Sauce

Name: Steamed Pacific Oysters with Mirin and Soy Sauce
Ingredients: 3 tablespoons light soy sauce; 4 shallots, finely sliced; 1 knob ginger, finely diced; ½ cup mirin; 3 shallots (white and green parts), finely sliced; 12 large unopened or freshly shucked Pacific oysters; 3 tablespoons rice wine vinegar