Preheat the oven to 400°F (200°C) and lightly grease a baking dish or line a sheet with parchment for easy cleanup.

Slice the kielbasa crosswise into ½-inch sections, stopping just before cutting through to create pockets that fan open while baking.

Whisk together mustard, honey, and smoked paprika until smooth, adjusting sweetness if desired.

Brush the glaze generously over the kielbasa, letting it seep into the slices.

Arrange in the dish and bake for 20–25 minutes until caramelized and golden.

Let cool slightly, then garnish with chopped parsley and serve warm while the glaze is still sticky and fragrant.