For the potstickers:
Place the pork mince and prawns into a bowl. Add the spring onions, garlic, ginger, soy sauce, sesame oil, rice vinegar, white pepper, sugar, cornflour, ground coriander, chilli flakes and smoked paprika. Mix thoroughly until the filling becomes slightly sticky and is evenly combined. Cover and refrigerate for 15–20 minutes. Place a dumpling wrapper on a clean work surface and spoon approximately 1 heaped teaspoon of filling into the centre of the wrapper. Lightly wet the edge of the wrapper with water, fold it over to form a half-moon and press firmly to seal. Pleat the top edge, if desired. Repeat with the remaining filling and wrappers.
To cook the potstickers:
Heat the vegetable oil in a large non-stick frying pan over medium-high heat. Arrange the potstickers flat-side down and cook, without moving them, for 2–3 minutes, until the bases are golden brown. Carefully pour in the water and immediately cover with a lid. Steam for 5–7 minutes, until the filling is cooked through. Remove the lid and allow any remaining water to evaporate, then cook for a further 1–2 minutes, until the bases are crisp again.
For the ponzu dipping sauce:
Combine the ponzu sauce, soy sauce, rice vinegar, sesame oil and honey or sugar. Stir in the spring onion, sesame seeds and chilli, if using. Serve alongside the hot potstickers.