Instructions:
- Heat the Dutch oven over medium heat. Add diced bacon/speck and render slowly until crisp. Remove bacon bits with a slotted spoon and set aside for garnish, leaving the rendered fat in the pot.
- Add onions, carrots, and celery to the pot. Sauté gently in the bacon fat for 8–10 minutes until softened and lightly golden. Add leeks and garlic; cook for another 2 minutes until fragrant.
- Stir in dried marjoram and cook for 30 seconds until aromatic.
- Add cubed potatoes, bay leaves, and pour in the stock. Bring the mixture to a boil, then immediately reduce heat to a gentle simmer. Cover partially and cook for 20–25 minutes, or until the potatoes are fork-tender.
- Remove the bay leaves. Use an immersion blender to carefully blend about half of the soup directly in the pot until smooth, leaving plenty of rustic texture.
- Stir in the heavy cream (if using) and apple cider vinegar. Season generously with salt and freshly ground black pepper, tasting carefully. Heat through gently—do not boil after adding cream.
- Ladle the Kartoffelsuppe into warm bowls. Garnish each serving generously with the reserved crispy bacon bits and a sprinkle of fresh parsley.