BBC Food - Recipes - Devilled herrings with green sauce

Ingredients

• 2 large free-range egg yolks
• 1 tbsp white wine vinegar
• 2 tsp Dijon mustard
• ½ tsp caster sugar
• ½ tsp flaked sea salt , plus extra to season
• freshly ground black pepper
• 150ml/5fl oz sunflower oil
• 1 small shallot , peeled and quartered
• ½ small garlic clove
• 1 tbsp small capers , drained
• 15g/½oz fresh parsley
• 15g/½oz fresh sorrel or basil
• 10g/¼oz fresh mint
• 10g/¼oz fresh tarragon
• 1 tsp freshly squeezed lemon juice
• 600g/1lb 5oz herring fillets (around 6 small-medium herrings , filleted)
• 750ml/1⅓ pint sunflower oil , for deep-fat frying
• 6 tbsp plain flour
• 3 tbsp semolina
• 2 tsp English mustard powder
• 1 tsp cayenne pepper
• 1 tsp fine sea salt
• ½ lemon , cut into wedges for squeezing