Preheat oven to 375°F.

Slice kielbasa into 1-inch pieces, then use chopsticks to make 1/4-inch hasselback-style slices on each piece without cutting all the way through.

Place sliced kielbasa in a baking dish.

Add brown sugar, ketchup, and horseradish to the dish. Stir to coat evenly.

Bake for 60–90 minutes, stirring every 20 minutes, until caramelized and edges are browned to your preference.

Serve warm and enjoy!