Peel and cut russet potatoes into 1-inch cubes so they cook evenly. Finely dice the onion, celery, and carrot. Mince the garlic. Reserve scallions/chives for garnish and to finish the soup.

In a large heavy-bottomed pot or Dutch oven, melt 3 tbs butter over medium heat until foaming.

Add the diced onion, celery, and carrot. Cook, stirring occasionally, until softened and translucent, about 6–8 minutes. Add the minced garlic and cook 30–45 seconds until fragrant.

Sprinkle the 3 tbs of flour over the softened vegetables and stir constantly for 1–2 minutes to cook the raw flour taste and form a roux. The mixture should thicken slightly but not brown.

Gradually whisk in 900 ml of chicken or vegetable stock, scraping up any brown bits from the bottom of the pot. Add the cubed potatoes, bay leaf, 1 tsp dried thyme, 1.5 tsp salt, and 0.75 tsp black pepper.

Bring to a gentle boil, then reduce heat to maintain a simmer. Cook uncovered until potatoes are very tender and easily mashable with a fork, about 15–20 minutes depending on cube size.

Remove and discard the bay leaf. For a creamier texture, use a potato masher to partially mash about one-third to one-half of the potatoes in the pot, leaving the rest in chunks. Alternatively, transfer half the soup (carefully) to a blender and purée until smooth, then return to the pot. If using a blender, vent steam slightly and work in batches.

Creamy Finish

Over low heat, stir in 250 ml whole milk and 120 ml heavy cream to the pot. Heat gently—do not boil—until the soup is warmed through and slightly thickened, about 3–5 minutes.

If using, whisk in 120 ml sour cream for a tangier finish. Taste and adjust seasoning with additional salt and pepper as needed.

Stir in 4 tbs thinly sliced chives/scallions (reserve some for garnish). Keep the soup on low while you prepare toppings.

Toppings / Garnish

Cook the 6 slices of bacon until crisp: either fry in a skillet over medium heat, bake on a sheet pan at 200°C (400°F) for 15–20 minutes, or microwave between paper towels until crisp. Transfer to a paper towel-lined plate and drain. Once cool, chop or crumble into bite-sized pieces.

Shred 1.5 cups sharp cheddar if not pre-shredded.

Ladle the soup into bowls. Top each bowl with a sprinkle of shredded cheddar (about 2–3 tbs per serving), a few crumbles of crispy bacon, and a pinch of the reserved sliced scallions/chives. Add freshly ground black pepper and salt to taste.

Serve immediately with crusty bread or crackers if desired.