2 salmon fillets , about 100g/4oz each
700g celeriac , peeled to remove all the knobbly skin and cut into chunks like potato
2 tsp wholegrain mustard
2 tsp lemon juice
100g baby spinach leaves
Brush the salmon lightly with olive oil, and season with salt and pepper. Line a grill pan with foil and lay the salmon on top.
Place the celeriac in a pan with cold water to cover.
Salt and bring to the boil. Lower the heat, cover and simmer for 12-15 minutes until tender.
Preheat the grill to medium. Whisk together the mustard, lemon juice, a pinch of sugar, salt, pepper and 1 tbsp olive oil.
Grill the salmon for five minutes on each side. Meanwhile, drain the celeriac, reserving 1 tbsp cooking water.
Return the celeriac to the pan. Mash until fairly smooth.
Add the spinach, stirring occasionally over a low heat, until wilted. Stir in 1 tbsp mustard dressing and the reserved cooking water. Season.
Spoon the mash on to two warm plates and top each with a fillet. Drizzle over the leftover dressing.