Peel and chop potatoes, finely chop chives, trim and slice fennel and thinly slice leek.
Heat olive oil in large heavy-based pot. Once shimmering, add fennel, leek and fennel seeds. Turn heat to medium and cook stirring for 10 minutes.
Add the stock and potatoes and bring to a boil, cover and simmer for 15 minutes.
Remove from heat and blend in three batches until smooth.
Return to the pan, add lentils, cream and ¾ of the chives. Season generously with salt and pepper then simmer until heated through (approximately 5 minutes).
Serve topped with reserved chives and accompanied by crusty bread.