Heat your Dutch oven over medium-high heat. Add the sliced kielbasa and cook 5-7 minutes, stirring occasionally, until the edges are nicely browned and some fat has rendered. Transfer to a plate with a slotted spoon, leaving the flavorful fat behind.

Reduce heat to medium. Add the diced onion to the pot and cook 4-5 minutes until softened and starting to turn golden at the edges. Stir in the garlic and cook 30 seconds until fragrant - do not let it brown.

Add the cubed potatoes, chicken broth, thyme, bay leaf, and black pepper. Stir well, scraping up any browned bits from the bottom of the pot. Return the kielbasa to the pot.

Bring to a boil, then reduce heat to maintain a gentle simmer. Cover partially and cook 18-20 minutes until the potatoes are fork-tender but not falling apart. Remove and discard the bay leaf.

Stir in the heavy cream and simmer 3-4 minutes more to heat through and slightly thicken. Taste and adjust seasoning - the kielbasa adds salt, so you may not need much. The soup should coat the back of a spoon lightly.

Ladle into bowls and top with chopped parsley. Add a dollop of sour cream if you like. Serve with crusty bread for dipping.