Place the kielbasa on a foil-lined baking sheet. Transfer to the oven and bake for about 7 to 8 minutes per side until nicely browned, to an internal temperature of 155°F (68°C) using a thermometer. While baking, cook the pierogies.
Add the pierogies to the boiling water and cook according to the directions on the package. Drain and set aside.
Heat a non-stick pan over medium heat.
Add the sauerkraut to the non-stick pan until warm. Drain the liquid and transfer it to a plate. Wipe out the pan and return to the burner.
Melt the butter in the pan. Once the butter starts to sizzle, brown the pierogies on both sides until they are golden brown.
Serve: place the kielbasa on a plate with the sauerkraut, pierogies, and sour cream. Enjoy with sparkling water.