Peel and chop the onion. Cut the bacon into small cubes. Peel the carrots and swede, cut them into bite-sized pieces.
Heat the oil in a large saucepan. Add the onion and bacon pieces, fry for 1-2 minutes, while stirring. Add the garlic, carrots and swede pieces. Sauté for about 5 minutes.
When the bacon starts to brown and the onion is soft, pour in the stock, add the rinsed lentils and add half of the lemon zest.
Bring to the boil then, at low temperature, simmer for 10 minutes.
Peel the parsnips and cut them into 2 cm pieces, then add these to the soup.
Simmer on a low heat for 25-30 minutes, then add half the parsley and take off the heat.
Using a hand-held blender, blitz for a few seconds, until you get a thick coarse soup.
Add the rest of the lemon zest and the garnish with the remaining parsley.
Serve with wholesome, crusty bread!