Combine the sauce ingredients in a small bowl and set aside.
Wash the green beans and drain them thoroughly.
Heat a wide deep skillet to high and add oil for deep frying. Add oil and bring the temp up to 375 degrees. Dredge the beans in the cornstarch in a large bowl,knock off any excess.
Deep fry the beans for 3-5 minutes, until their skins begin to wrinkle but still crisp. Remove from the oil and drain on paper towels.
Heat a separate deep skillet or wok to high and add 2 Tbsp of the frying oil. When you see a few whisps of white spoke, stir in preserved vegetable, garlic, and ginger and brown for 30 second or until fragrant. Add the beans to the pan, folding constantly for about 30 seconds. Stir in the sauce and fold into the beans until well combined. Cook for about 1 minute until all the ingredients are thoroughly combined.
Serve and enjoy!