Place sliced beef in a large bowl. Grind fresh black pepper over the beef, a good 10-12 turns. Mix meat to distribute pepper and repeat peppering process, about 6-7 turns of the grinder.
Mix cornstarch, soy sauce and black vinegar together until smooth. Pour mixture over peppered beef and mix to evenly coat. Set aside to marinate.
In a separate bowl, mix together chicken broth, oyster sauce, sesame oil and peanut butter. Use a whisk to combine. Set aside.
Heat wok over high heat until hot. Turn heat down to medium high and add 2 tablespoons of the oil. Swirl it around the pan to coat then add the beef. Stir fry the beef until no longer pink, 3-4 minutes. Remove beef and set aside.
Add remaining tablespoon of oil to the skillet, swirl, then add the snap peas. Stir fry for 1-2 minutes then add the garlic and ginger. Stir fry another minute then add the water chestnuts. Stir fry 1 minute.
Add beef back into vegetables in wok and stir. Whisk the peanut sauce then pour into pan and stir. Allow sauce to boil for a minute then reduce heat and simmer until sauce thickens. When sauce looks like it's almost done, add the scallions and stir to distribute. Cook one minute longer then serve over your favorite rice.