First of all, peel and chop the onion finely. Toss it on a heated pan with melted butter and fry until golden brown. Toss it in a pot.
Clean potatoes, peel and dice them, chop the leek finelyand then put them in a pot with fried fried onions add broth and water. Bring it to boil and cook over medium heat for 20 minutes. Take out potatoes, crush them using a blender and put the potato puree back to the broth. Mix it well over low heat and add marjoram, parsley, thyme and few drops of hot sauce. Finish it with salt and pepper to taste.
Serve with croutons