In large skillet, cook bacon over medium heat 8-10 minutes until crispy. Transfer to paper towels, cool, then crumble. Save 2 tablespoons bacon fat.
Peel and dice potatoes into 1-inch chunks. In skillet with bacon fat, cook diced onion 3-4 minutes until softened. Add garlic and cook 1 minute until fragrant.
Place potatoes in bottom of 6-8 quart slow cooker. Layer onion-garlic mixture over potatoes. Sprinkle half the crumbled bacon over top.
Pour in chicken broth and water. Liquid should just cover potatoes. Sprinkle ranch seasoning packet over everything.
Cover and cook on LOW for 6-7 hours or HIGH for 3-4 hours until potatoes are fork-tender and starting to break down.
Using potato masher or immersion blender, mash about half the potatoes in the crockpot. Leave some chunks for texture. Don’t over-mash.
Stir in softened cream cheese until completely melted and smooth, about 2-3 minutes. Add sour cream, heavy cream, and butter. Stir gently until combined and heated through.
Gradually stir in shredded cheddar in three batches, letting each melt before adding more. This prevents clumping.
Stir in remaining bacon, saving some for garnish. Taste and adjust salt and pepper. Let heat through 10-15 minutes with lid on.
Ladle into bowls and top with extra cheese, bacon, chives, sour cream, and red pepper flakes if desired.
Notes
Soften cream cheese to room temperature before adding to prevent lumps.
Use low-sodium broth to better control final salt level.
Don’t lift slow cooker lid during cooking or you’ll add time.
Soup thickens considerably when refrigerated. Add milk or broth when reheating.
Can substitute Russet potatoes but Yukon Golds provide better texture and flavor.