In a measuring cup, whisk together soy sauce, water, cooking wine, brown sugar, and corn starch. Set aside.
In a skillet, over medium-high heat, add vegetable oil. Once oil is heated, add minced garlic and cook until fragrant. Add the snow peas and cook until bright green, about 3-4 minutes. Remove from skillet and set aside on a plate.
Add the flank steak to the skillet and cook until mostly cooked through, about 5-7 minutes.
Add the snow peas back into the skillet then pour sauce in. Let simmer and thicken for 3-5 minutes, stirring and tossing to incorporate everything.
Serve with white rice.
Video
Notes
If you don't have michiu Chinese cooking wine, you can use mirin, which is Japanese cooking wine.