Boil potatoes untill 3/4 done. Drain and cool. Fry bacon in skillet untill crispy.
In the skillet you fried the bacon in; heat oil and saute onion,carrot and celery. Add flour and continue cooking. If necessary adjust flour and oil until smooth paste is formed(roux). Cook untill roux has turned a light golden brown. Add milk slowly whisking to keep smooth. Keep whisking and warming until mixture tightens up. Add salt and pepper to taste. Combine all ingredients and cook on low for 15-20 minutes or until warm.
It is best to have your milk slightly warm instead of cool when making the roux. I like to add granulated garlic and smoked chipotle chili powder to the roux. Also a bit of your favorite shredded cheese and diced green onion never hurts.