How to Make It
In a large pot, cook the bacon strips until crisp. Remove the bacon with a slotted spoon and drain on paper towels. Discard all but 2 tablespoons of the bacon fat or, if there's less than 2 tablespoons, add enough olive oil to make up the amount.
Reduce the heat to moderately low. Add the onion to the pot and cook, stirring occasionally, until translucent, about 5 minutes.
Add the lentils, salt, pepper, rosemary, bay leaf, and water to the pot. Bring to a boil. Reduce the heat and simmer, partially covered, stirring occasionally, for 15 minutes. Add the cauliflower florets and simmer, stirring occasionally, until the cauliflower and lentils are tender, about 15 minutes longer. Remove the bay leaf.
Stir the parsley into the soup. Serve the soup topped with the bacon.
Variation Substitute broccoli florets for the cauliflower. Add them after the lentils have cooked for about twenty-five minutes and then simmer until the broccoli is tender, five to ten minutes longer.