Handful of fresh flatleaf parsley, chopped (optional)
Cook the puy lentils in the vegetable stock in a covered saucepan for 20-25 minutes until tender. Drain, discarding the stock, then put in a serving bowl.
Whisk the lemon juice with the olive oil and Dijon mustard. Whisk in the sugar, then season with salt and freshly ground black pepper. Pour over the bowl of warm lentils, then add the grated lemon zest and the crème fraîche or double cream. Scatter with the flaked hot-smoked salmon and chopped parsley, if using. Toss gently to combine, then serve.