In a small bowl, mix together the soy sauce, rice wine vinegar, brown sugar, oyster sauce, and sesame oil. Set aside.
Heat the vegetable oil in a wok or large skillet over high heat and add the shrimp and stir fry until pink (about 2 minutes). Remove from wok and set aside.
Using the same pan, add in the garlic and ginger and stir to combine. Cook for about a minute.
Pour in the sherry. Stir it around, scraping the bottom of the pan to loosen all the flavorful bits that may have stuck to the wok. Cook for about 2 minutes to cook off the alcohol.
Turn the heat to medium-low and pour in the sauce mixture, then mix in the cornstarch mixture. Stir the sauce for 1 to 2 minutes to thicken, then add the cashews and pepper (to taste). stir to coat everything with the sauce. You can add a little water if the sauce looks too thick. Add the shrimp to the sauce.
Sprinkle on the green onions. Serve with cooked rice.