In a large saucepan, cook bacon over moderate heat until crisp. Remove bacon, reserving drippings. Drain bacon on paper towels; set aside. Add leeks and garlic to reserved drippings and cook until tender. Add potatoes, broth, salt, and pepper. Bring to a boil. Lower the heat and simmer, covered, for 20 minutes or until potatoes are tender. Using a fork, slightly mash the potatoes against the side of the saucepan.

In a medium-sized bowl, wisk together the milk, flour or potato flakes, and basil; stir into potato mixture. Cook over moderate heat, stirring constantly, until mixture starts to thicken. Cook and stir 2 minutes more or until thickened. Ladle soup into bowls. Top with bacon. Serve with corn bread. Makes 6 side-dish servings.