Start by heating a large stockpot over medium heat. Add a tablespoon of olive oil. Once hot, toss in the diced onion, chopped celery, and sliced carrots.

Stir frequently. Sauté for about 5-7 minutes until softened. The smell will fill your kitchen, and I dare you not to sneak a taste!

Next, add the Italian sausage, breaking it apart with a spoon. Let it cook for about 5 minutes. You want it nicely browned. The fat from the sausage will infuse the veggies and add a depth of flavor.

Once the sausage is browned, it's time to add the minced garlic. Sauté for another minute until fragrant. Then, mix in the diced zucchini. Let it cook for about 3-4 minutes until the zucchini softens.

Pour in the lentils and diced tomatoes, including their juices. Add the chicken stock and balsamic vinegar. This is where the magic starts to happen. Stir everything to combine, and bring it to a boil.

Once boiling, reduce the heat to low. Season with salt, pepper, dried basil, oregano, thyme, and red pepper flakes to taste. Simmer uncovered for 30-40 minutes. Stir occasionally, allowing the flavors to meld beautifully.

After 30-40 minutes, check the lentils; they should be tender but hold their shape. If the soup looks a bit thick, add a splash more stock or water for your desired consistency. Taste and adjust seasoning if needed. Serve hot, garnished with fresh parsley.