In a large pot, heat 2 tablespoons of olive oil over medium heat until shimmering. Add 1 chopped onion and sauté for about 5 minutes, stirring frequently, until it turns soft and translucent. Stir in 2 minced garlic cloves, 1 teaspoon of dried thyme, and 1 teaspoon of cumin (if using), cooking for an additional minute until fragrant.

Add 1 cup of brown or green lentils, along with 2 diced carrots and 2 medium diced potatoes, into the pot. Mix the ingredients well to ensure the lentils and vegetables are evenly coated with the aromatic base.

Pour in 6 cups of vegetable broth (or water), then add 1 bay leaf. Increase the heat and bring the soup to a rolling boil. Once boiling, reduce the heat to low and let it simmer gently for 25-30 minutes, stirring occasionally, until the lentils and potatoes are tender yet still holding their shape.

Carefully remove the bay leaf. Taste the soup and adjust the seasoning with salt and pepper. For a creamier texture, gently mash some of the cooked potatoes and lentils against the side of the pot using the back of a spoon.

Ladle the warm soup into bowls, and garnish with freshly chopped parsley. If desired, add a dollop of yogurt or sour cream for an extra creamy finish. Serve alongside crusty bread.