Begin this recipe three days ahead to pickle the
4long bread rolls (about 19cm long), halved lengthwaysMelted butter, for brushing2 cupstorn mixed soft herbs, such as basil, dill and flat-leaf parsley½thinly sliced Spanish onionExtra-virgin olive oil, to tasteAïoli, to serve2whole smoked trout, skin and bones discarded, flesh flaked150 gmPersian feta, crumbledPickled cauliflower1small cauliflower (about 650 gm), broken into florets1fennel bulb, thinly sliced3salad onion bulbs, thinly sliced1 tbspolive oil1½ tspyellow mustard seeds500 ml (2 cups)apple cider vinegar140 gmcaster sugar1 tbspsea salt flakes80 gmsultanas1 tspfinely grated ginger4small green chillies (optional)
For pickled cauliflower, blanch cauliflower and fennel until tender but still crisp (1-2 minutes; see cook’s notes p184). Drain, rinse briefly under cold water to cool slightly and shake off excess water. Place in a bowl along with salad onion. Heat oil in a saucepan over medium-high heat, add mustard seeds and stir until seeds pop (10-20 seconds). Add vinegar, sugar, salt and 200ml water and bring to a simmer. Add sultanas, ginger and chillies, then pour mixture over cauliflower. Place in a sterilised jar, seal and store in a cool dark place or refrigerate for 3 days before using. Pickles will keep up to 3 months.
Brush cut sides of bread halves with butter and fry cut-side down in a large non-stick frying pan until golden and toasted (2-3 minutes).
Combine herbs, onion and olive oil to taste in a bowl. Spread bases of rolls with aïoli, then top with smoked trout, herb salad and feta. Season to taste, sandwich with tops of bread and serve with cauliflower pickles.