Boil potatoes, leeks, celery.
In a large pot, add cubed potatoes, sliced leeks, roughly chopped celery, and chicken broth and bring to boil. Boil on medium heat until the ingredients are soft. About 15-20 minutes. While this is boiling, preheat oven to 375° (190°C). Lay bacon on wire rack over another baking pan and bake in oven until brown and crisp (about 10-15 minutes). Check if your veggies are done by inserting a fork into a potato. If it’s soft to the point where it just disintegrates when you stick the fork in, the next step you go.
Using a ladle, transfer half the mixture into a food processor (or blender) and blend until smooth. Make sure you ladle equal amounts of the ingredients and broth. Be careful, the mixture will be HOT. Place a towel over the food processor/blender and your hand on top of the cover to keep it shut. Transfer blended mixture to large bowl and set aside while you blend the second batch. If your food processor/blender isn’t big enough, you can do this in three batches. Don’t overflow the blender. Transfer all of the puréed mixture to a large bowl and set aside.
In the pot, melt butter and add flour over medium heat to make a roux, whisking until butter and flour are incorporated to form a paste. Slowly add in milk a little at a time while whisking until all the milk is added. Keep whisking as you bring the mixture to the a boil and it will start to thicken. The mixture should have the consistency of gravy. Add grated montery jack cheese a cup at a time while whisking until cheese is melted and incorporated.
Add potato mixture.
Take the potato mixture you set aside and add that back into the pot into the mornay sauce. Stir to combine well. Cook on low-med heat for another 5 minutes to get all the flavours incorporated. If the soup is too thick, you can add a bit more milk to thin it out.
When the crispy bacon has cooled, break it up into small pieces and chop using a mincing motion. Ladle the soup into soup bowls and garnish. To get the whipping cream to float on the surface of the soup and not sink to the bottom, pour it into a mixing bowl, and using a whisk, whisk until it begins to bubble a little, about a minute. What you are essentially doing is whipping air into the cream so that it floats. Drizzle over soup and top with chopped chives and bacon dust. Congrats! You just made potato jack leek soup.