In a large soup pot or Dutch oven, cook the bacon over medium heat until crisp. Remove cooked bacon and set aside on a paper-towel lined plate.
Using the same pot with bacon fat remaining in the bottom, saute the white parts of the scallions (reserving the green parts for topping), shallots and the 4 cloves of minced garlic and red pepper flakes. Heat till just golden brown, about 2 minutes, stirring frequently so that the garlic does not burn. (To make this recipe vegetarian, omit the bacon and saute vegetables in 3 Tbsp butter.)
Add the diced potatoes, milk, onion powder and Kosher salt. Bring to a boil over medium to medium-high heat. As soon as it starts to boil, reduce heat to low and simmer, covered, for about 10-15 minutes until the potatoes are tender.
Once potatoes are tender, remove from heat and briefly pulse mixture in batches in a blender or food processor. (Remember to keep the lid slightly opened on blender to avoid steam building up inside the blender cup.) You can also do this entire process right in the pot with a potato masher, if you prefer.
Stir in the sour cream, ¼ of the bacon (reserving the rest for topping) and cheddar cheese. Stir until combined.
Serve in bowls topped with bacon, cheddar cheese, a dollop of sour cream and chopped scallion greens.