Haddock rarebit & celeriac mash

Cut away the celeriac skin and discard, then cut the flesh into chunks. Put into a pan of lightly salted boiling water with the potato and boil for 12-15 minutes until tender. Put the cheese, mustard, Worcestershire sauce and chopped thyme into a small saucepan.

Pat the fish dry with kitchen paper, then lightly season. Melt half the butter in a frying pan and fry the haddock for 2 minutes each side. Lift onto a plate. Add the onion to the pan with the remaining butter and fry gently for 5 minutes until golden. Preheat the grill to medium.

Push the onions to one side and return the haddock to the pan. Spoon the onions on top. Briefly melt the cheese mixture in the saucepan and spoon over the onion. Grill for 1-2 minutes, until the cheese is bubbling and the fish is opaque and flakes easily with a fork.

Drain the celeriac and potato, then return to the pan. Add the milk and plenty of black pepper, then mash well. Spoon onto plates, top with the haddock and scatter with the remaining picked thyme leaves. Serve with green vegetables or seasonal leaves, if liked.