Heat heavy-bottomed saucepan over medium heat. When pan is hot, add diced bacon and fry bacon until crisp. Transfer crisp bacon to plate lined with paper towels and set aside.
Pour out all but 1 tablespoon bacon grease from saucepan. Add diced onion to reserved bacon grease and stir well, then cook over medium heat until onion is softened and translucent, approximately 5 minutes.
Add minced garlic and cook, stirring constantly, until garlic is fragrant, approximately 30 to 60 seconds.
Slowly pour in chicken stock, then add cubed potatoes. Stir well, then bring mixture to boil and cook approximately 12 minutes or until potatoes can be easily pierced with fork.
When potatoes are ready, reduce heat under saucepan to low. Carefully tilt saucepan to one side and ladle out 1 ½ cups of liquid directly into blender. Be careful not to add any potatoes or onions to blender if possible. Add raw cashews to blender with soup liquid and carefully blend on high speed until cashew mixture is completely smooth, approximately 60 seconds.
Use potato masher to mash potatoes in saucepan to desired consistency. For chunkier potato soup, leave some potatoes completely unmashed.
Pour cashew mixture into saucepan, then pour in almond milk. Stir well and let soup simmer over low heat until warmed through. Season with sea salt and black pepper to taste. If soup is too thick, stir in additional chicken stock until desired consistency is achieved.
Ladle prepared soup into serving bowls. Top with crisp bacon pieces, chopped chives, and additional black pepper if desired. Serve warm.