Peel and dice the russets into even pieces; chop the onion, carrots, celery and slice the leeks. Mince the garlic and crumble cooked bacon; grate the cheddar and chop parsley so everything is ready for smooth workflow.

In a large pot over medium heat, melt the unsalted butter. Add the onion, leeks, carrots and celery and sauté until softened and beginning to color, about 6–8 minutes.

Add the diced potatoes, minced garlic, and dried thyme to the pot. Pour in the vegetable or chicken broth, bring to a simmer, and cook until potatoes are fork-tender, about 12–15 minutes.

For a chunkier soup, gently mash some potatoes with a potato masher. For a creamier texture, use an immersion blender to puree part or all of the soup.

Reduce heat to low and stir in the heavy cream and shredded cheddar cheese until melted and smooth. Season with salt and freshly ground black pepper to taste.

Ladle into bowls and garnish with chopped parsley and crumbled bacon. Add extra cheddar or a drizzle of olive oil if desired.