This is a standard oyster sauce (not Thermomix converted):
Bring to a boil, then simmer in a covered pot for 30 minutes: 2 C fresh oysters + 3 C water + 1 C bottled clam juice + 1 teaspoon salt + 1 clove of garlic + white portion of 1 green onion + 1 slice of fresh ginger root, then add a mixture of 1/4 C soy sauce + 1 teaspoon sugar + 2 teaspoons cornstarch + 3 tablespoons water, and simmer for 10 more minutes, stirring occasionally, then strain out the solids in the sauce and discard (the solids)