Combine the mayonnaise, lime juice and half of the sour cream in a bowl. Season and add coleslaw mix and chopped coriander. Stir to combine. Place the taco spice mix in a sealable plastic bag. Add the prawns. Seal the bag and shake to coat prawns. Heat oil in a frying pan over high heat. Cook prawns, in two batches, for five minutes or until prawns curl and change colour. Meanwhile, heat the tortillas in microwave following packet directions. Place tortillas on a serving platter. Spoon coleslaw into tortillas. Top with prawns and remaining sour cream. Drizzle with the mild taco sauce and sprinkle with coriander leaves. Serve with lime wedges.