In a large pot, heat 2 tablespoons of olive oil over medium-high heat. Add the chopped onion, minced garlic, and diced celery, sautéing for about 2-3 minutes until the onion becomes translucent and fragrant.

Add the cubed potatoes and sliced carrots to the pot, seasoning lightly with a pinch of salt. Sauté for another 1-2 minutes.

Stir in the rinsed green or brown lentils, dried thyme, and marjoram. Pour in 6 cups of vegetable stock.

Once boiling, reduce the heat to low and cover the pot. Allow the soup to simmer for 25-30 minutes, stirring occasionally.

After simmering, let the soup cool for about 5 minutes. Use an immersion blender to blend a portion of the soup until smooth.

Stir in the shredded cheddar cheese until it melts into the soup. Adjust the seasoning with additional salt or pepper as desired.

Ladle the soup into bowls, garnishing with fresh herbs. Serve with crusty bread or a side salad.