Knead all-purpose flour and warm water into a soft dough; rest for 20 minutes.
Heat oil and sauté garlic paste, finely minced cabbage, carrot, and mushroom for 2 minutes.
Season filling with soy sauce, black pepper, and salt; let cool.
Roll dough into thin translucent wrappers, place filling in center, and pleat edges to seal.
Steam dumplings in a steamer for 10 minutes until glossy and served hot.