Measure out all beans and lentils. Rinse them thoroughly under cold water to remove any dust or debris.

(Optional but recommended) Place the rinsed beans and lentils in a large bowl, cover with plenty of water, and soak overnight. This helps soften the beans and reduces cooking time. If you skip soaking, expect a slightly longer simmer.

Drain and discard the soaking water. Transfer the beans and lentils to a large soup pot.

Add 10–12 cups of fresh water or broth to the pot. Use more liquid for a thinner soup, less for a thicker consistency.

If using, add the optional ingredients: minced garlic, diced onion, bay leaf, thyme, carrots, celery, and ham. These add extra flavor and heartiness.

Place the pot over medium-high heat and bring the mixture to a boil.

Once boiling, reduce the heat to low and cover the pot with a lid, leaving a small gap for steam to escape.

Simmer gently for 1.5 to 2 hours, stirring occasionally. Check the beans for tenderness after 1.5 hours; continue simmering if needed.

Skim off any foam or impurities that rise to the surface during cooking.

When the beans are tender and the soup has thickened to your liking, season with salt to taste. (Adding salt at the end helps prevent the beans from toughening.)

(Optional) For a bright finish, stir in 1 tablespoon of vinegar just before serving.

Remove the bay leaf before serving. Ladle the soup into bowls and enjoy hot.