In a large heavy bottomed pot over medium heat, cook the bacon until crisp, stirring occasionally, about 10 minutes. Remove bacon to a paper towel lined plate and set aside, but do not clean out pot.
Add onion to pot and cook until softened, stirring frequently, about 4 minutes. Add garlic and red pepper flake and cook until fragrant, just about 1 minute.
Add green beans, chicken broth, and a pinch of salt and bring to a boil. Cover, and reduce heat to a simmer. Let simmer until green beans are very tender, 45 minutes to 1 hour.
Check liquid level occasionally and add more broth if needed.
Add butter and bacon to the pot and stir to combine until butter has melted. Season to taste with salt and pepper and serve. Enjoy!