Finely chop the shallot and ginger.
Juice the oranges, then scrape out the flesh.
Heat the oil in a wok or large frying pan and stir-fry the shallot, ginger and garlic for a minute.
Add the orange juice, soy sauce and orange flesh.
Let it bubble for a few seconds, then add the langoustine and cava.
Put a lid on, turn up the heat and cook for 3-5 minutes until they change colour.
Remove them to plate, then reduce the sauce by half.
Strain this sauce through a sieve into a small bowl or jug. If it’s not thick enough, reduce it further over high heat.
Serve the langoustine with the sauce on the side.