Prepare the fish

Thaw the grass carp completely. If it has already been coated with cornstarch, leave the coating intact. Otherwise, lightly coat the fish with about 1½ tsp cornstarch.

Heat the wok

Heat a wok or frying pan over medium-high to high heat. Add the oil.

Stir-fry the grass carp

Add the fish in a single layer. Leave it undisturbed for about 1–2 minutes so the cornstarch coating can set.

Turn gently

Flip the pieces and cook for another 1–2 minutes, until lightly coloured and almost cooked through. Avoid tossing too aggressively because the fish can break apart. Remove and set aside.

Reheat the leftovers

Add the leftover cauliflower and all of its remaining sauce to the same wok. Add 1–2 tbsp water or stock if the sauce has become thick in the fridge.

Bring everything up to temperature

Stir-fry until the vegetables and sauce are thoroughly reheated and the sauce is simmering.

Return the fish

Add the grass carp back to the wok. Gently fold it through the cauliflower rather than vigorously stir-frying.

Finish

Cook for another 30–60 seconds, or until the fish is just cooked through and coated in the original sauce.

Taste before seasoning

The takeaway sauce may already provide enough seasoning. Only add a small splash of light soy sauce, salt or white pepper if it actually needs it.