20 asparagus spears, woody ends removed
1 tbsp snipped fresh chives
3 tbsp chopped fennel fronds
2 garlic cloves, finely chopped
1 garlic clove, finely chopped
80g/2¾oz fresh horseradish, peeled and grated (or 2 tbsp creamed horseradish)
1–2 tsp creamed horseradish
1 lemon, zest and juice, plus two lemons, halved, to serve
3 tbsp chopped fresh mint
500g/1lb 2oz new potatoes, boiled and cooled
1 banana shallot, peeled and finely chopped
3 tbsp chopped fresh tarragon
1 tbsp chopped fresh tarragon
2 tbsp chopped fresh thyme
3 tbsp mayonnaise
sea salt and freshly ground black pepper
2 tbsp olive oil
250g/9oz unsalted butter, softened
4 mackerel fillets (about 400g/14oz each), butterflied, scales removed and pin-boned