Into your slow cooker insert, drop the chopped russet potatoes, chicken broth, canned cheddar cheese soup, chopped onion, minced garlic, salt, and black pepper, stirring firmly to thoroughly dissolve the cheese soup paste into the broth. Clamp the lid tight and set the slow cooker to High for 3 to 3 ½ hours or Low for 4 to 6 hours until the potato cubes are completely tender and slide effortlessly off a fork.

Exactly 30 minutes before the slow cooker cycle ends, take off the lid and use a potato masher or the heavy back of a ladle to mash roughly 50% of the potato chunks right inside the liquid. Leaving half the potatoes intact preserves rustic chunks, while smashing the rest releases loose amylose starch molecules straight into the hot chicken broth, naturally bodying and thickening the soup liquid without straining or dulling its flavor.

Immediately after mashing, create a stabilizing liaison roux by melting 4 tablespoons of butter in a medium saucepan over medium heat, whisking in the ¼ cup of flour to cook for 60 seconds to strip away the raw flour flavor, and slowly streaming in the 2 cups of half-and-half while whisking aggressively until the mixture turns into a glossy, thick, double-cream paste.

Pour this hot half-and-half liaison straight into the bubbling slow cooker, drop in the sour cream and exactly 1 cup of your freshly shredded cheddar cheese, and stir continuously for 2 minutes until unified. Dairy fats can easily break down and curdle if subjected to hours of intense crockpot heat, so whisking the cream with a small flour-and-butter roux before adding it cushions the delicate dairy proteins, keeping your soup velvety and uniform rather than separated and watery.

Secure the slow cooker lid back in place and let it finish cooking on low heat for the remaining 30 minutes, stirring occasionally, then ladle the hot soup into deep bowls and blanket each serving generously with the remaining 1 cup of shredded cheddar cheese, the crispy crumbled bacon, and a heavy scattering of fresh green onions.