Any kind of beef may be used, but flank steak works particularly well because it is easy to cut across the grain, which helps keep the meat from falling apart during stir-frying and produces a tender result.
Be sure to serve plenty of rice, as it helps moderate the hot chilies without detracting from the flavor.
You may reduce the number of chilies by up to one half if you prefer less heat, but traditionally this dish should have a rich, hot chili flavor.
To prepare ahead: You can proceed through Step 5, omitting the mint or basil leaves. Store the mixture in the refrigerator. When ready to serve, heat the mixture and add the leaves. If the meat has absorbed the liquid, add just enough warm water to bring it back to the original consistency.