For a great alternative to the traditional seafood/cocktail sauce I like to make a Sriracha Mayo.
All you need is a bottle of Japanese Mayo (Kewpie) and a bottle of Sriracha (Thai chilli sauce).
Place some mayo into a bowl and whisk in some Sriracha to taste, you can also squeeze in some lime juice if you wish but this is optional.
Enjoy with some fresh prawns and a glass of wine!
