Start the soup: Set a large soup pot or Dutch oven on the stove over medium heat. Add the olive oil and let it warm for about 30 seconds.

Soften the vegetables: Add the sliced leek, diced carrots, diced celery, and 1 teaspoon of the salt to the pot.

Soften the vegetables: Cook the vegetables for 6 to 8 minutes, stirring often, until the leek is soft and the carrots have started to lose their raw look.

Build the base: Add the chopped garlic to the pot. Cook for 1 minute, stirring, until it smells fragrant.

Build the base: Put the potato pieces into the pot. Stir for about 1 minute so they get coated with the oil and vegetables.

Build the base: Add the lentils to the pot and stir once more so they are mixed through the vegetables.

Add the broth: Pour the vegetable broth into the pot. Use a spoon to scrape the bottom of the pot so nothing is stuck there.

Add the broth: Raise the heat to medium-high and bring the broth to a boil.

Simmer until the lentils start to soften: Lower the heat so the soup bubbles gently. Leave the pot partly covered and simmer for 20 minutes.

Finish the stew-like texture: Add the drained chickpeas to the pot. Stir them in well.

Finish the stew-like texture: Keep simmering for 10 to 12 minutes more, until the lentils are tender and the potatoes are very easy to pierce with a fork.

Thicken the soup: Use a potato masher or the back of a large spoon to mash some of the potatoes and some of the chickpeas right against the side of the pot. Mash just enough to thicken the soup a little while still leaving plenty of chunks.