In a large pot over medium-high heat, add a splash of olive oil and let it warm for about a minute. Sauté the chopped onion and celery until they become soft and translucent, approximately 5-7 minutes. Stir in the minced garlic and continue cooking for another 1-2 minutes until fragrant.

Toss in the cubed potatoes and chopped carrots, seasoning them with a pinch of salt. Stir everything together and cook for an additional 1-2 minutes, allowing the vegetables to start softening.

Stir in the rinsed green or brown lentils along with the thyme and marjoram. Pour in the vegetable stock and bring the mixture to a boil. Once boiling, reduce the heat to low, letting it simmer gently for 25-30 minutes, until the lentils are tender yet not mushy.

After simmering, remove the pot from heat. For an added creamy texture, take out a quarter of the soup and blend it with shredded cheddar until smooth. Mix this back into the pot.

Taste your soup and adjust the seasonings as needed. Serve warm, topped with fresh herbs and a dollop of sour cream or dairy-free sour cream if desired.