Whisk the flour, salt, and sugar together. Rub in the cold butter with your fingertips until it looks like coarse breadcrumbs. In a separate bowl, whisk the egg, water, and vinegar, then pour into the flour mixture. Mix with a fork, then bring together into a rough dough — don't overwork it. Wrap and chill for 30 minutes.

While the dough chills, heat the oil in a pan and sauté the onion, carrot, and potato until softened and starting to turn golden, about 7 minutes. Add the chicken and cook until no longer pink, about 5 minutes. Pour in the water and soy sauce, cover, and simmer until the vegetables and chicken are tender, around 10 minutes.

Remove from heat and stir in the chopped curry cube until fully dissolved. Return to low heat and simmer, uncovered, stirring often, until the mixture is thick enough to hold its shape on a spoon with no liquid pooling. This takes about 8 minutes and is what stops your empanadas from leaking or splitting in the air fryer.

Spread the filling on a tray and refrigerate until completely cool — at least 30 minutes.

Roll the chilled dough to about 3mm thick and cut into 12–14cm rounds. Spoon a heaped tablespoon of cold filling into the centre of each. Brush the edge with egg wash, fold into a half-moon, and press firmly to seal. Crimp with a fork or pleat by hand for the classic edge.

Rest the sealed empanadas in the fridge for 15 minutes before frying — this helps the seal hold.

Preheat the air fryer to 180°C (356°F). Brush both sides of each empanada with egg wash and sprinkle with black and white sesame seeds. Air fry in a single layer, not touching, for about 14 minutes, flipping halfway, until deep golden and crisp.

Let rest for a couple of minutes before serving - the filling is very hot straight out of the air fryer.

Serve with Japanese Mayo if desired.