Pre-heat oven to 400°F.
In a large pot over medium-high heat cook the bacon with the oil. When the bacon is nice and crispy remove the bacon from the pot.
Add the celery and onions to the bacon fat and cook to take the raw flavour off of them. About 1-2 minutes. Remove the vegetables and set aside for later.
Add the flour to the fat. Stir consistently and let cook for 1-2 minutes.
Whisk in the milk and bring to a simmer to thicken.
Turn down the heat to low and add the potatoes, cream, celery and onion. Let the potatoes cook for 15-20 minutes until soft.
While the soup is cooking, combine half of the crispy bacon with the parmesan. Spread the bacon-parm mix into long fingers, about 5” long, onto a parchment lined sheet pan. Place into oven and bake until golden brown, about 7-9 minutes.
Add to the soup the sour cream, green onions and crispy bacon. Adjust the seasoning with salt and pepper. Let cook for another 10 minutes for the flavours to come together.
Place the soup into a bowl and serve with the crisps