Pink ling burgers

Ingredients

• Vegetable oil, for deep-frying
• 1 egg
• 2 tsp milk
• 80g rice flour
• 25g panko (Japanese-style) breadcrumbs
• 4 x 120g ling fillets, skin removed, pin-boned
• 4 brioche buns, cut in half horizontally
• 8 baby cos lettuce leaves
• 2 whole pickled onions, sliced into rings
• 2 pickled cucumbers, thinly sliced lengthways
• 100g tartare sauce