Instructions:
- Render the Bacon: Heat the Dutch oven over medium heat. Add the diced bacon/speck and cook slowly until the fat is rendered and the bacon is crispy. Remove the crispy bacon with a slotted spoon and set aside for garnish. Leave about 2 tablespoons of the rendered fat in the pot.
- Sauté Aromatics: Add the chopped onion, carrots, and celery to the bacon fat. Sauté gently for 8–10 minutes until the vegetables begin to soften (sweat them, do not brown them).
- Simmer the Potatoes: Add the cubed potatoes, broth, bay leaf, and thyme sprigs to the pot. Season lightly with salt and pepper. Bring the mixture to a boil, then immediately reduce the heat, cover, and simmer for 20–25 minutes, or until the potatoes are completely fork-tender.
- Remove Aromatics: Discard the bay leaf and thyme sprigs from the soup base.
- Blend for Smoothness: Use an immersion blender to carefully purée the soup directly in the pot until it reaches your desired consistency.
- Enrich and Balance: Stir in the heavy cream (if using). Heat gently. Taste the soup, then stir in 1 tablespoon of the white wine vinegar. Taste again and add the second tablespoon if necessary to balance the richness.
- Serve: Ladle the hot soup into bowls. Garnish generously with the reserved crispy bacon bits and fresh parsley.