Peel potatoes and soak in a large bowl for about 30 minutes to an hour. This will help pull the bad starchy water from out of it.
Cut into large chunks (about 1"-2" each). Dice half of a large yellow onion. Mince 3 cloves of garlic. If using bouillon powder, prep in a bowl of hot water (this will cook in the crockpot). Cut butter into cubes.
Fill crockpot with potato, onion, garlic, chicken broth, butter, salt and pepper. If using salted butter, use less salt to season. Stir a few times to combine.
Cook on High for 4 hours. After 3.5 hours, pull 1/2 cup to 2 cups of the broth out. For thicker soup, pull more broth out. For thinner soup, leave more broth in. If you pull too much, add water in 1/2 cup at a time until the preferred consistency is obtained. Use your hand immersion blender to mix everything to your preference. If you would like to have some of the potatoes and onions intact, only blend about 2/3-3/4 of the pot.
Let cool slightly before serving.