Rinse 1 cup of lentils thoroughly under cold water in a colander to remove any debris.

Slice 1 leek (white and light green parts only), ensuring it's well-rinsed to remove dirt.

Peel and dice 2 carrots and 1 parsnip, one celery stick and cube 2 medium potatoes.

Mince 3 cloves of garlic, and if using, slice 6 oz of kielbasa.

Heat 2 tablespoons of olive oil in a large pot over medium heat.

Add the sliced leeks and cook for about 3-4 minutes until softened.

Stir in the garlic, carrots, celery and parsnip, cooking for another 2-3 minutes to develop flavor.

Once the veggies are tender, stir in tomato paste and cook for about 1-2 minutes. This helps to caramelize the tomato paste slightly, enhancing its depth of flavor and reducing any raw taste.

Transfer everything to a large stock pot. Add in 1 teaspoon of marjoram, 1 teaspoon of smoked paprika, 2 bay leaves, and 4 allspice berries (or a pinch of ground allspice).

Pour in 6 cups of broth and bring to a gentle boil.

Add the rinsed lentils and potatoes, stirring to combine.

Lower the heat to a gentle simmer and cook uncovered for 25-30 minutes, or until the lentils and vegetables are tender.

If the soup thickens too much, add more broth as needed.

If using kielbasa, sauté it in a separate pan until lightly browned, then stir it into the soup.

If using bacon, crumble it and sprinkle it on top just before serving for a crispy texture.

Stir in 1 tablespoon of apple cider vinegar to brighten the flavors.

Season with salt and pepper to taste, adjusting as needed.