In a large bowl, stir salt into water until dissolved. Add prawns and set aside 5 minutes. Rinse prawns and dry on paper towels.
In a small bowl, mix together stock, rice wine, soy sauce, cornflour, sugar and pepper. Set aside.
Heat 1 tablespoon oil in a large frypan or wok over high heat. Cook prawns, turning constantly, until pink on all sides, about 1 minute. Stir in garlic, ginger and 2 teaspoons oil. Stir in snow peas, chives and 1/4 teaspoon salt; stir-fry 1 minute more.
Stir stock mixture into frypan and continue cooking until sauce thickens. Serve immediately.