For the sauce, in a small bowl combine the soy sauce, cornstarch, sherry, brown sugar, ginger and garlic. Reserve 2/3 of the sauce for later, using the rest to marinate the sliced meat (cover and let marinate in fridge for 45 minutes).
Add 2-3 Tbsp of water to a wok or skillet and bring to a boil. Add broccoli, cover and cook for 2-3 minutes until tender crisp. Remove from pan and set aside.
Drain any water and allow water to evaporate completely from pan. Add oil and heat until almost smoking. Drain marinade and sear meat for about 1 minute on each side, do this in several batches, otherwise too much moisture will be released from the meat and you’ll steam rather than sear it. Remove from pan and set aside.
Pour the reserved sauce into the skillet, along with beef broth and oyster sauce. Bring to a boil and allow to reduce until thick. Once the sauce is the thickness you like, stir in the broccoli, beef and baby corn, tossing to coat.