Saute onions and leeks in a stock pot on medium to medium high heat, until the onions begin to soften. Add water to the pan, as needed to prevent sticking.
2 large sweet onions, 2 leeks
Add garlic and saute for 1 minute.
6 cloves garlic
Add potatoes and cook for about 10 minutes, covered. Check on them and if they're sticking, add a little water.
6 cups Yukon Gold potatoes
Add water and cook on medium low for about 25 minutes, until the potatoes have started to break down.
3 cups water
Add milk and bring back to a low boil for about 5 minutes. If you less chunks, you can use a potato masher or immersion blender to mash the soup a bit.