Cook the salsify in a pan of boiling salted water for 6-8 minutes, or until tender. Drain and refresh in cold water, then pat dry with kitchen paper.
Whisk the 100ml/3½fl oz olive oil and the sherry vinegar together in a bowl and add the ground black peppercorns.
Bring a pan of water to the boil and reduce to a simmer. Drop the egg yolks into the water one at a time and poach gently for a minute, or until just set on the outside. Remove with a slotted spoon and drain on kitchen paper.
Heat a frying pan until hot and add the remaining tablespoon of olive oil and the butter. Fry the salsify for 2-3 minutes, turning occasionally, until tender. Season with the smoked salt.
To serve, divide the dressed rocket evenly among four serving plates, then place a stick of salsify on each plate. Carefully place the poached egg yolk next to the salsify and shave over the parmesan cheese. Drizzle over the olive oil and sherry vinegar dressing and serve immediately.