Source: Benihana/TVFN

1 cup soy sauce
1/2 cup sake
5 teaspoons ketchup
1 cup granulated sugar
1/3 cup cornstarch, dissolved in 1/3 cup water
1 cup Mirin
Juice of 1 freshly squeezed apple or 3 tablespoons apple juice
1 pinch black pepper

Combine first seven ingredients in saucepan and cook for 10 minutes over medium heat.

Gradually stir in dissolved cornstarch solution until mixed well. Stir well before serving. May be stored in the refrigerator for up to one week.