Dice potatoes, carrots, celeriac and parsley root into fairly small cubes (about 1 cm). Cut leek in 1 cm rings.
Sauté the veggies in vegetable oil. Add lentils and vegetable stock (note: lentils should be well covered!), season with soy sauce, pepper, and some vegan sugar (I use at least one teaspoonful). Add the laurel leaves and cook. In a pressure cooker, this takes about 20 minutes.
When cooked, take out the laurel leaves and discard them, add the vinegar (to taste) and tomato paste if desired.
This is a variation of a traditional German recipe. If you want to be traditional you can serve this with a vegetarian sausage - but it is nice by itself, and particularly good for a cold winter day.