1. Heat a Dutch oven over medium heat. Add oil to pan; swirl to coat. Add pancetta; cook 1 minute or until pancetta begins to brown, stirring occasionally. Add onion and next 4 ingredients (through bay leaf); cook 8 minutes or until vegetables are tender, stirring occasionally. Add lentils, broth, and 2 cups water; bring to a boil. Cover, reduce heat, and simmer 40 minutes or until lentils are tender and mixture is slightly thickened. Remove from heat. Discard bay leaf.
2. Place 2 cups lentil mixture in a blender. Remove the center piece of blender lid (to allow steam to escape), and secure blender lid on blender. Place a clean towel over opening in blender lid (to avoid splatters), and blend until smooth. Return pureed lentil mixture to pan. Add baby spinach, chopped basil, Parmesan cheese, lemon juice, and black pepper; stir until spinach wilts. Serve immediately.