Prep the potatoes: Peel and dice the potatoes into small, even cubes. Smaller pieces cook faster and blend smoothly.
Load the crockpot: Add potatoes, onion, garlic, broth, salt, pepper, thyme, smoked paprika, and bay leaf to the slow cooker.
Stir to combine.
Cook low and slow: Cover and cook on Low for 6–8 hours or on High for 3–4 hours, until the potatoes are very tender.
Remove bay leaf: If you used one, take it out before mashing or blending.
Thicken the soup: Add butter and milk (or cream). Use a potato masher to mash some of the potatoes directly in the pot, or use an immersion blender for a smoother texture. Leave some chunks if you like it rustic.
Add creaminess: Stir in sour cream (or Greek yogurt) and cheddar until melted and smooth.
Taste and adjust salt and pepper.
Serve and top: Ladle into bowls and top with extra cheddar, bacon, and green onions. Serve hot.