Mussels with cider, leek and Arran mustard

Method

Melt 25g butter in a heavy-bottomed pot over medium heat and sweat the shallot until translucent, approximately 3 minutes. Add the sliced leeks and cook gently for a further 5-6 minutes, stirring occasionally, until softened but retaining texture. Pour in the dry cider, add thyme sprigs, bay leaf and crushed peppercorns, then bring to a gentle simmer. Add the prepared mussels, cover with a tight-fitting lid and steam for 4-5 minutes until the shells open, shaking the pot once halfway through cooking; discard any mussels that remain closed. Remove from heat and strain the cooking liquor through fine muslin into a separate saucepan, reserving approximately 150ml; gently remove one mussel shell from each specimen and discard, leaving the mussels in their other shells. Whisk the Arran mustard and remaining 25g cold butter together to form a smooth paste, then whisk this into the strained cooking liquor over low heat until fully incorporated. Add the double cream and warm through gently without boiling, tasting and seasoning with sea salt as needed. Return the mussels in their shells to the sauce with the cooked leeks, toss gently, and distribute between shallow warmed bowls. Finish with a scattering of fresh parsley and chive batons, and serve immediately with good crusty bread for soaking up the sauce.