In a large skillet, fry the bacon and place onto paper towels to drain. Reserve 2 tablespoons of the bacon grease and discard the rest.
In the reserved bacon grease, cook the onions and celery until tender. Add the minced garlic cook 1-2 minutes more.
To the slow cooker, add the stock, vegetable mixture, salt, pepper, dry mustard, dried tarragon, and garlic powder. Whisk to combine.
Add the potatoes and set the slow cooker for 8 hours on low until the potatoes are tender.
Just before serving, use an immersion blender to smooth out the potato soup to desired taste.
Stir in the heavy cream and shredded Gruyere cheese. If desired, add in the sour cream.
Serve with crumbled bacon pieces and cheddar cheese for topping.
Notes
This soup is also delicious when garnished with fresh parsley, chives or scallions.Variations:If you prefer not to use bacon, cook the onions and celery in butter.For a little crunch, melt 1 tablespoon of butter in a skillet on medium heat, add ½ cup of panko bread crumbs and toast. Add to the top of the soup in lieu of bacon.