Place jalapeño, spring onion, garlic, spices, oil vinegar and tomato in a bowl, season with salt and pepper and toss to combine.
Place avocado and lime juice in a bowl, season with salt and pepper and mash with a fork.
Heat char grill or BBQ over medium high heat.
Brush prawns with oil and chargrill 2-3 min each side or until cooked through.
Spread bottom half of buns with sour cream and avocado.
Top with prawns and spoon over pico de gallo. Sandwich with remaining bread tops and serve with hot sauce and corn chips.