Slice the meat into 1/4" thick strips of bite sized pieces. Put in a bowl and sprinkle with 1 Tbs of soy sauce and sherry, mix together, and let sit for a quick marinade.
Slice the broccoli into florets. Slice any thick stems into 1/4" pieces.
Mix together the cornstarch, water, 4 tsp soy sauce, sesame oil, ginger, and garlic. If you want it spicy, add some red pepper flakes, 1/2 tsp or so.
Heat 2 Tbs of oil in a skillet over medium high. When it's hot, add the beef, stirring frequently. Cooked meat will only take a minute or two. Raw meat should cook in 3-4 minutes. Remove the meat.
Add the other 1-2 Tbs oil and then cook the broccoli 2-3 minutes, until softened a bit. Put the meat back in the pan. Reduce the heat a bit, pour in the cornstarch mix and stir together. Cook 2-3 minutes.