Preparation Simmer lentils, water, broth, bay leaf, and half of garlic in a 4-quart pot, uncovered, 12 minutes. Meanwhile, heat oil in a wide heavy 5- to 6-quart pot over medium-high heat until it shimmers. Brown sausage, about 7 minutes. Transfer sausage with a slotted spoon to a bowl. Reduce heat to medium and cook onion, carrots, celery, remaining garlic, 1 teaspoon salt, and 1/2 teaspoon pepper, stirring occasionally, until softened, about 5 minutes. Stir in tomato paste and cook, stirring, 2 minutes. Add sausage and lentils with cooking liquid and simmer, uncovered, until lentils are tender, 3 to 5 minutes. Stir in escarole and cook until tender, about 3 minutes. Stir in vinegar to taste and season with salt and pepper. Discard bay leaf.
Preparation Simmer lentils, water, broth, bay leaf, and half of garlic in a 4-quart pot, uncovered, 12 minutes. Meanwhile, heat oil in a wide heavy 5- to 6-quart pot over medium-high heat until it shimmers. Brown sausage, about 7 minutes. Transfer sausage with a slotted spoon to a bowl. Reduce heat to medium and cook onion, carrots, celery, remaining garlic, 1 teaspoon salt, and 1/2 teaspoon pepper, stirring occasionally, until softened, about 5 minutes. Stir in tomato paste and cook, stirring, 2 minutes. Add sausage and lentils with cooking liquid and simmer, uncovered, until lentils are tender, 3 to 5 minutes. Stir in escarole and cook until tender, about 3 minutes. Stir in vinegar to taste and season with salt and pepper. Discard bay leaf.