Combine the first 5 ingredients in a bowl. Add the prawns and toss coat. Cover and marinate the prawns at room temperature 30 minutes. Preheat your grill to medium-high. Grill the prawns 1 to 2 minutes per side, or until nicely charred and just cooked through. Set the prawns on platter and season with salt. Garnish with lime slices, set the platter on the table, and allow your guests to peel and eat the prawns.