Cook the bacon in a large Dutch oven over medium heat until browned and crispy. Set it on paper towels to drain the grease. Chop into crumbles; set aside until needed.
Add the leek and green onions to the same Dutch oven over medium-high heat and cook, stirring occasionally, for 4-5 minutes. Add the garlic and crushed red pepper flakes and cook, stirring constantly, for 1 minute.
Add the diced potatoes and broth then season with sea salt and freshly cracked pepper, to taste; bring to a boil then reduce heat to medium and cook until the potatoes are very tender, about 20-25 minutes.
Transfer to a blender and blend until creamy. You can also use an immersion blender if you'd prefer.
Return the soup to the pot and add milk and kale then cook over medium heat, stirring occasionally, for 5 minutes or until the kale has wilted. Taste and season with sea salt and freshly cracked pepper, to taste, as needed.
Ladle into bowls and serve with bacon crumbles on top. Enjoy.