Knead all-purpose flour and warm water into a soft, smooth dough; rest for 20 minutes.
Heat oil in a skillet and stir-fry garlic paste, finely chopped cabbage, carrot, and spring onion for 2 minutes.
Season filling with soy sauce, black pepper, and salt; cool completely.
Roll dough into small thin wrappers, place filling in center, and pleat to seal.
Steam dumplings for 10 minutes in a greased steamer until wrappers are glossy.