Dice ½ cup onion and 1 cup sliced celery, mince 2 cloves garlic, and slice 2-3 carrots into rounds.
Cut 1½ cups diced cooked ham into bite-sized pieces. Add 1½ cups dried lentils to a fine mesh strainer and rinse well under cold water to wash the lentils.
Next, heat 2 tablespoons olive oil in a Dutch oven over medium heat. Add the onion, garlic, celery, and carrots and sauté just until softened slightly, about 4–5 minutes.
Stir in the 15 ounces canned diced tomatoes, 6 cups vegetable stock or chicken broth, lentils, ham, 1 teaspoon dried thyme, and 1 bay leaf. Lower the heat to low and cover the Dutch oven.
Allow the soup to simmer, covered, for about 35-45 minutes, or until the lentils are completely softened and cooked through. Test near the end of the cook time to see how softened they are.
Stir in an additional 2 cups vegetable stock or chicken broth to achieve a soup consistency. Season Salt and pepper to taste sprinkle with Fresh parsley for garnish, and serve.
Video
Notes
Keep extra broth handy. Lentils continue absorbing liquid as the soup sits, so don't worry if it looks thicker than expected. You can always stir in a little more broth to get the consistency you prefer.