I make a fantastic potato-leek soup. I got the recipe from a Thomas Keller book. I won't copy the entire recipe, but I'll give you the gist of it and you can find something similar.
I make stock from scratch. Canned stuff is usually way too salty. If you can find low-sodium stock, go for it. I've used lamb stock, beef stock, and veal stock and all work well.
1/2 white onion
3 large leeks
1 carrot
2 russet potatoes
3 shallots
4 cloves garlic
1/2c heavy cream
fresh herbs wrapped in cheesecloth (thyme, italian parsley, whole black pepper, 2 bay leaves)
Blacken the flat side of the onion by putting it in a frying pan over medium heat and letting it char. Take it out and dice it.
Peel and chop all of the vegetables. Put the potato pieces (about 1 inch cubes) in a bowl of cold water.
In a large saucepan, pour a little bit of olive oil over medium heat. Add the onions, garlic, shallots, and leeks, and sweat them until they're all wilted. Pour in your stock (about 3-4 qts), and bring to a simmer. Once simmering, add the carrots. Rinse the potatoes and add them as well. Bring to a simmer, add the herbs. Simmer for 40 minutes to an hour, or until the potatoes are soft.
After the potatoes are done, reduce the heat and add some salt to taste. Adding too little won't change the flavour at all, adding too much will make it salty, adding just the right amount will bring out a lot of flavours without making anything salty.
Remove the soup from the heat, and transfer it to a blender in batches. Blend it good until it's really smooth, and then pour through a strainer (you may have to force it a little) into a clean bowl. Once the original saucepan is empty, wash it, put the blended and strained soup back into it, and bring it to a simmer again. Reduce it a little bit until it's as thick as you want it (it should be pretty good actually), or add a bit more stock if it's too thick.
Add the 1/2c cream and bring back to a simmer, then remove from the heat.
Pour into a bowl, drizzle with a little olive oil (walnut oil is especially nice if you want to go nuts), drizzle a little cream on it as well, then crack some fresh black pepper and maybe some freshly chopped chives as well.
