1. In a bowl, mix together the soy sauce, sherry, cornstarch, brown sugar and ginger. Add the beef to a separate bowl and pour one-third of the liquid over the top. Save the rest of the liquid. Toss the beef and set aside.
2. Heat the oil in a heavy skillet (iron is best) over a high heat. Add the snow peas and stir for 45 seconds and get as much color on them as possible. Remove to a plate.
3. Allow the skillet to get very hot again. With tongs, add half the meat mixture, leaving most of the marinade still in the bowl. Spread out the meat as you add it to skillet, but do not stir for a good minute. (You want the meat to get as brown as possible in as short amount a time as possible.)
4. Sprinkle half the spring onions over the meat. Flip the meat to the other side and cook for another 30 seconds. Remove to a clean plate.
5. Repeat with the other half of the meat, allowing the skillet to get very hot again first. After flipping, add the first plateful of meat, the reserved liquid, the crushed red pepper and snow peas. Stir over high heat for 30 seconds, and then turn off the heat.
6. Check seasonings and add salt only if it needs it. The mixture will thicken as it sits. Serve immediately over rice.