- Blanch the celeriac in boiling water for 5 – 6 minutes, drain and pat dry. Brush with the rapeseed oil and season generously.
- Heat a griddle pan until very hot, add the celeriac and chargrill on each side for 1–2 minutes. Lift onto a plate and keep warm.
- Heat the smoked mackerel in the griddle pan. Alternatively, just remove the skin, check for small bones then flake.Toss the chicory, radicchio and iceberg together and pile into a serving dish.
- Place the ingredients for the dressing in a food processor and whiz until it forms a paste similar to pesto. Season well with salt and freshly ground black pepper.
- Arrange the celeriac and the smoked mackerel on the leaves and drizzle with the hazelnut dressing to serve.