Place the oil-filled pot over medium high heat and bring the oil to 375°F. Line a bowl or baking pan with paper towels and set aside.

Finely chop (or cut into 1/8-inch cubes) the kielbasa then transfer it to a small mixing bowl. Super finely mince the sauerkraut and onions then add those along with the Cheddar cheese to the mixing bowl with the kielbasa. Toss to evenly distribute and set aside.

In a large mixing bowl, combine the corn meal, flour, salt, sugar, baking soda, black and cayenne pepper with a whisk. In a separate bowl, use the same whisk to thoroughly combine the butter, yogurt or buttermilk and egg. Pour that directly into the flour mixture, add the kielbasa mixture, and use a spatula to stir everything together gently, just until no more dry pockets remain and it is combined evenly.

Use a 1 1/2 teaspoon scoop (or simply mound the batter on a teaspoon) to drop the batter into the hot oil. Fry only as many as can comfortably fit into the pan while leaving room for them to move around and expand as they cook. Don't overcrowd that pan! Fry the hush puppies for 2-3 minutes per batch, flipping them about halfway through the cooking. Use tongs or a slotted spoon to transfer the finished hush puppies to the paper towel lined bowl or pan and let drain briefly before serving.

These are best when served hot, but are still great warm or room temperature. You can store leftover hush puppies in a paper towel lined, tightly covered container in the refrigerator and reheat them for just a few minutes in a hot oven to re-crisp them.