Place diced potatoes in a large pot and cover with chicken broth. Bring to a rolling boil over medium-high heat, then reduce heat to medium and simmer for about 15 minutes until potatoes are fork-tender and beginning to break apart at the edges.

While potatoes cook, remove a small bowl from heat. Whisk together flour and 3 tablespoons of heavy cream until smooth with no lumps. This prevents clumping when added to hot soup.

Once potatoes are tender, add butter to the pot and stir until melted. Slowly pour in flour mixture while whisking constantly for 1-2 minutes until soup thickens and coats the back of a spoon.

Pour in remaining heavy cream and let simmer together for 5 minutes at medium heat. Keep heat at medium to prevent boiling, which could break the cream.

Reduce heat to medium-low and stir in sour cream, cheddar cheese, garlic powder, onion powder, salt, and pepper. Stir gently until cheese melts completely and soup becomes smooth. If soup breaks or appears curdled, whisk in 1/4 cup fresh cream off heat until smooth.

Ladle into bowls and top generously with extra shredded cheddar, crumbled bacon, and fresh green onions. Serve immediately while hot.