Cured Leatherjacket with Horseradish Vinaigrette

Ingredients

• 2 leatherjacket fillets (about 190gm each), or other white-fleshed fish such as snapper or blue-eye, skin removed
• 55 gm sea salt
• 45 gm caster sugar
• 1 spring onion, thinly sliced
• Thinly sliced mustard leaves, miner's lettuce and borage flowers, to serve (see note)
• Toasted seeds
• 2 tbsp sunflower seeds
• 1 tbsp sesame seeds
• 1 tbsp nigella seeds
• 2 tbsp buckwheat
• 250 ml vegetable oil (1 cup)
• Horseradish vinaigrette
• 50 gm finely chopped onion
• 1½ tbsp rice vinegar
• 1½ tbsp light soy sauce
• 1 tsp finely grated horseradish
• 1 garlic clove, thinly sliced
• 70 ml grapeseed oil
• 1 tbsp sesame oil