In a large heavy-bottomed pot over medium heat, add diced bacon. Cook until the fat renders and bacon is crisp, about 6–8 minutes. Using a slotted spoon, remove most of the bacon to a bowl leaving about 1 tablespoon of bacon fat in the pot. Add butter to the pot and melt. Add diced onion, carrot, and celery and sauté until translucent and soft, about 6–7 minutes. Add minced garlic and cook 30–45 seconds until fragrant.

Make roux

Reduce heat to medium-low and sprinkle flour over the softened vegetables. Stir constantly for 1–2 minutes to cook the raw flour taste and form a light roux. The mixture should be pasty and a little golden but not browned.

Add stock and simmer

Gradually whisk in the chicken (or vegetable) stock until fully incorporated and smooth. Increase heat to medium-high and bring to a gentle simmer. Add diced potatoes. Simmer until potatoes are tender, about 12–15 minutes.

Purée (optional)

For a silkier soup, use an immersion blender to purée about half the soup until slightly thickened but still retaining some texture. Alternatively, transfer up to half the soup to a blender, puree, and return to the pot. Stir to combine.

Add dairy

Lower heat to medium-low. Stir in heavy cream and milk, warming gently but not boiling, for about 3–4 minutes.

Whiskey & Flavorings

Temper and add whiskey

To avoid a sharp alcohol bite and hot spots, remove the pot from direct heat for 1 minute. Slowly add the whiskey in a steady stream while stirring. Return to low heat and simmer gently for 4–6 minutes to let some alcohol cook off and flavors meld. Do not boil vigorously once cream is present.

Add seasoning

Stir in apple cider vinegar, Dijon mustard, Worcestershire sauce, and brown sugar. Taste and adjust the balance of sweet, tang, and salt. Simmer on low for another 2 minutes.

Proteins & Vegetables

Finish with bacon, spinach and thyme

Return the reserved crisp bacon pieces to the pot. Add the baby spinach and fresh thyme leaves; stir until the spinach wilts, about 1–2 minutes. If the soup seems too thick, add up to 1/2 cup additional stock or water to reach desired consistency.

Finishing & Garnish

Season and serve

Season the soup with salt and freshly ground black pepper. If desired, add a splash of lemon juice to brighten the flavors (about 1 teaspoon). Ladle soup into bowls and garnish with chopped chives and an extra crumble of bacon if reserved. Serve warm.