Dough: In bowl, divide flour into 2 mounds. Pour 1/3 cup/75 mL boiling water over one of the mounds, stirring with fork, until combined. Stir oil and salt into remaining mound.

Slowly pour in 1/3 cup/75 mL cold water, stirring mounds together with fork until in shaggy dough, adding up to 3 tbsp/45 mL more water if necessary.

On lightly floured surface, knead until smooth. Wrap in plastic wrap; let rest at room temperature for 30 minutes.

Filling: In large bowl, lightly beat egg with 2 tbsp/30 mL water; add beef, onions, soy sauce, hot pepper, ginger, sesame oil, salt and pepper, and thoroughly mix.

On lightly floured surface, roll dough into log. Cut into 12 slices; flatten each into disc and cover with tea towel or plastic wrap. One at a time, uncover each disc and roll into 5-inch/12 cm circle; spoon scant 1/4 cup/60 mL filling in centre. Gather edge of dough around filling; pinch together at top, twisting off extra dough. Flatten dumpling slightly.

(Make-ahead: Cover and refrigerate for up to 8 hours. Or freeze in airtight container for up to 1 month; do not defrost. Fry frozen.)

In nonstick skillet, heat half of the oil over medium heat; add half of the dumplings, tops up and at least 1/2-inch/1 cm apart. Add enough water to come three-quarters of the way up sides of dumplings, about 1 cup/250 mL.

Cover and cook over high heat until water evaporates, about 6 minutes. Reduce heat to medium; uncover and fry until bottoms are golden and crusty, about 5 minutes. Repeat with remaining oil and dumplings.

Dipping Sauce: Mix vinegar with soy sauce; divide among small saucers. Sprinkle with sesame seeds (if using). Serve with chili paste or chili oil (if using), on side, to add to sauce.

Makes 12 dumplings.