Combine rice wine or sherry, soy sauce, sugar and cornstarch in a large bowl
Add steak strips and marinate for about 6 to 8 hours, stirring occasionally
Heat a large frying pan or wok then add about 1 Tbsp of oil and bring to moderate heat
Add green pepper squares and stir-fry for a few minutes until crisp tender
Remove green pepper squares with slotted spoon and reserve
Add about 3 to 4 more Tbsp of oil to pan and bring to very high heat
Add ginger and cook for a few seconds; then add the steak mixture
Stir fry for about 4 to 5 minutes until meat is no longer pink
Add pepper squares and cook for a minute or so and then serve with hot rice