Cook and crumble the bacon, reserving two tablespoons of bacon grease.
Heat the bacon grease and butter in a large pot over medium temperature. Add the diced onions, chopped carrots, and chopped celery. Saute for 2-3 minutes.
Stir in the flour, salt, and black pepper. Cook while stirring for 2 minutes.
Pour in the chicken broth and whole milk. Stir until the flour is dissolved.
Add half of the crumbled bacon (reserve the remaining bacon for garnish) and the diced potatoes. Bring the soup to a boil and then reduce heat and simmer for 12-15 minutes until the potatoes are tender, stirring occasionally.
Top with shredded cheddar cheese, reserved crumbled bacon and sliced chives.