In a stock pot cook the bacon over medium-high heat until done. Add the onions and cook until soft and translucent and golden, 7-10 minutes. Add the garlic and cook for another minute. Add the celeriac, leek and carrots and cook for another 4-5 minutes or until beginning to soften. Add the lentils and cook for another minute or two. Add all remaining ingredients except for the parsley and bring to a boil. Reduce the heat to medium, cover and simmer for 30 minutes.
Stir in the parsley and add salt and pepper to taste.