Melt butter in a stock pot over medium heat.
Add garlic and saute for 30-60 seconds until fragrant.
Add flour to pan.
Slowly add milk a little at a time while whisking constantly to eliminate lumps. Whisk until smooth and then add chicken broth.
Bring soup to just a simmer and heat until thickened, stirring often, about 5 minutes.
Once soup has thickened, turn heat down to medium low.
Cut potatoes in half length-wise and use a spoon to scoop out potato flesh into the pot. Use a wooden spoon to smash potatoes breaking up large clumps.
Add 1 1/2 c. grated cheese, salt, pepper, and stir until cheese is melted.
Remove pan from heat and stir in 3/4 c. sour cream, and 1/4 c. green onions.
Add additional salt and pepper to taste.
Ladle into bowls and top each serving with the remaining sour cream, onions, cheese, and bacon.