Add the vinegar, stir a little, and pour in the stock. Bring to the boil.
Add the garlic, cooked lentils (save some for garnishing) and cauliflower then cover and simmer for 30 minutes.
Remove from the heat and blend using a stick blender.
Serve the fennel soup with a dollop of yoghurt, some sour cream or shaved parmesan, sprinkled with the crumbled pancetta, a spoonful of lentils and snipped fennel leaves
Recipe by Sugar Plum Sisters at https://sugarplumsisters.com/2015/10/fennel-leek-soup/