Saute' the leeks in the olive oil until they become very soft and a little translucent.
In a large soup pot, combine the cooked leeks, chopped potatoes, chicken broth, bouillon cube, onion powder, garlic powder, herbs de provence and marjoram.
Bring to a rolling boil and reduce heat to medium. Stir frequently.
Cook until the potatoes are completely soft and mushy. (As if you were making mashed potatoes)
Remove the pot from heat.
Blend the entire thing until smooth, using a hand blender (this is the cleanest and easiest method), or by transferring everything from the pot to a blender.
NOTE: This is a thick soup. If you want a thinner soup, simply add more chicken stock.
Notes
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible.