Cajun fried shrimp

Name: Cajun fried shrimp
Ingredients: 500g extra-large raw king prawns (the biggest raw king prawns in the supermarket are often in the frozen section), defrost thoroughly, peel if needed, then pat dry with kitchen paper – if buying from a fishmonger, ask them to peel and de-vein them for you; 1 tbsp hot & herby Cajun spice mix (see below); 284ml tub buttermilk; 100g polenta; 100g cornflour; 1 tsp mustard powder; 4 tbsp mayonnaise; 1 tbsp hot sauce; 2 tbsp paprika; 4 tsp garlic powder; 4 tsp cayenne pepper; 2 tsp ground black pepper; 2 tsp onion powder; 1 tsp dried thyme; 1 tsp dried oregano