In a bowl, mix flank steak, corn starch, baking soda and oil. Set aside for 15 minutes to tenderize the meat.
In a large skillet or wok on medium high heat, add 2 tbsp. oil and sear the beef in batches. Set aside.
Add in long green peppers and onions and stir fry for 3 minutes.
Add in remaining ingredients and toss the beef in. Stir fry for 2 minutes.
Notes
Place the steak in the freezer for 1 hour or until partially frozen. This will firm up the meat and make it easier to slice the steak into thin pieces.
Slice against the grain to ensure tenderness.
Adjust the amount of Sichuan peppercorns to your taste!