Step 1

Fry the bacon in a large pot over medium heat, stirring frequently, until the fat is rendered and the bacon is crisp, 4 to 5 minutes. Add the olive oil, onions, celery, carrots, and garlic and cook, stirring occasionally, until the onions are soft and translucent, about 5 minutes. Do not brown; reduce heat if necessary. Add the tomatoes (with their juices), broth, lentils, thyme, bay leaves, salt and pepper and bring to a boil. Cover partially, reduce the heat to low, and simmer until the lentils are tender, 45 to 50 minutes (see note on cooking time if using common brown or green lentils). Fish out the bay leaves and discard.

Step 2

Use an immersion blender to purée the soup until the broth is slightly thickened, or to desired consistency. (Be careful not to purée too much or the soup will get too thick, and you'll lose the integrity of the lentils.) If you don't have an immersion blender, transfer about 2 cups of the soup to a blender and purée until smooth, then return the blended soup to the pot. Garnish with fresh chopped parsley if desired and serve. (Note: The soup may thicken as it sits; thin with a bit of water if necessary.)

Step 3

Note: If using common brown or green lentils instead of French lentils, start checking for doneness around 30 minutes.

Step 4

Make-Ahead/Freezing Instructions: You can prepare this soup up to 3 days in advance, or freeze it for up to 3 months for longer storage. To defrost, let the soup thaw in the refrigerator overnight. When ready to serve, reheat the soup on the stovetop over medium heat until it's thoroughly hot. If you find the soup has thickened more than you'd like during its time in the fridge or freezer, simply stir in a little water or broth to reach your desired consistency.