Fill a stockpot with enough water to cover the potatoes. Add ½ tsp salt and the potatoes. Cook for 8 to 10 minutes, or until the potatoes are tender when pierced with a knife. Drain and set aside.
In a Dutch oven, cook the bacon until crispy. Remove the bacon and set aside, leaving 1 tablespoon of bacon grease in the pot.
Add the butter to the Dutch oven with the bacon grease. Saute the onion in the mixture until soft. Add the garlic and cook for one more minute, or until fragrant.
Stir in the flour and cook for a minute, then gradually whisk in the milk and chicken broth. Bring to a gentle boil.
Add the drained potatoes to the pot. Season with additional salt (if needed) and ¼ tsp pepper, or adjust to taste.
Stir in the sour cream, shredded cheddar cheese, and half of the cooked bacon. Bring to a simmer, then remove from heat.
Garnish with the remaining bacon and chopped green onions before serving.