Rinse and slice the leek. Heat the oil in a small/medium pot and throw the leek in. Saute fo 2-3 minutes. Meanwhile, rinse and dice the potato(the smaller the potatoes the quicker they cook). Add the potato to the pot altogether with vegetable stock and water.
Cover with a lid and bring to a boil. Reduce heat to low and simmer covered until the potatoes are ready (about 10 minutes).
Puree the soup with immersion blender (or a food processor/blender) until creamy. Taste it and season with salt and pepper.
Serve warm or chilled.
Notes
Extra virgin olive oil can be substituted with cooking olive oil/sunflower/vegetable oil or real butter. I recommend using either olive oil or butter for the best flavor.
I used shot glasses that hold about 1 fluid ounce/35 milliliters of liquid. This is enough to fill 14 shot glasses. You can also choose larger glasses to serve this soup in but in this case I recommend doubling the recipe.
I used dry measuring cups to measure the liquids.
Half and half can also be added to this soup to make it more creamy, if desired.
If you feel the soup is too thick, add more water or stock.
Make sure to season the soup at the very end as every stock contains a different salt level.