Dice one large onion (and celery, if using) and place in the bottom of a large stockpot with approximately 1 Tbsp of oil and/or butter. Cook over medium heat, stirring regularly until cooked (approximately 10 minutes).

Wash, peel, and cut potatoes and carrots into large pieces.

Add the vegetables to the pot and cover with water (approximately 4-6 cups). Add stock cubes according to directions on the box (we use 1 cube per 2 cups of water). Bring the mixture to a boil and switch to a low simmer. Leave it for at least an hour or as long as you wish.

Remove soup from heat source and let it stand for a few minutes. Mix/blend soup together until smooth using an immersion hand blender or a stand blender.

Serve the soup with a small handful of shredded cheddar cheese in each bowl, and stir to combine into the hot soup.