2 wild salmon fillets , about 140g/5oz each
2 tsp wholegrain mustard
squeeze lemon juice
1 small celeriac , about 350g/12oz, peeled and cubed
1 floury potato , peeled and cubed
140g frozen peas
Line a grill pan with foil and lightly brush with oil to stop the salmon sticking.
Add the salmon and spread each fillet with 1 tsp mustard.
Curl up the edges of the foil to catch any juices, then squeeze over a little lemon juice. Heat the grill to medium.
Boil the celeriac and potato for 15 mins. Add the peas, then cook for a further 5 mins until the vegetables are tender. Meanwhile, grill the salmon for 12-15 mins.
Drain the vegetables, reserving a cup of the cooking water, then mash roughly so that the peas start to break up.
Add a little of the cooking water to loosen the mix, if you like. Season to taste, then divide between two warm plates and top with the salmon.
Pour over any pan juices, then serve.