Simple. Try it once, make it forever.
For 4 people
2 big leeks
1 vegetable stock cube
1 tablespoon of olive oil
Peel and chop the onion. Wash the leeks and cut them in slices. Peel the carrots and cut them in slices. Peel the potatoes and cut them in 6-8 pieces.
Heat a big pan with the olive oil on medium heat.
Once hot add the onion and let it cook for 5 minutes.
Add the carrots and leeks for 2 minutes. Then cover and cook for 5 more minutes.
Boil water. Add the water in the pan to cover the vegetables.
Cook for 25 minutes with the lid at low heat.
Mix (I use a hand blender like this).