Start by bringing a large pot of water to a rolling boil over high heat. Carefully add the mini pierogies, cooking them for about 3 minutes or until they float to the surface. Use a slotted spoon to remove them and set aside.

In a large skillet, melt 2 tablespoons of butter over medium-high heat until bubbling. Add the sliced kielbasa and sauté for about 5-7 minutes until golden-brown and crisp.

Remove the browned kielbasa from the skillet and set aside. Add 3 tablespoons of butter to the skillet and stir in the coarsely chopped onions, cooking for about 5 minutes until soft and translucent.

Return the browned kielbasa back to the skillet along with the prepared pierogies. Gently toss everything, cooking for an additional 3-4 minutes on medium heat until warmed through.

Remove from heat and transfer the pierogies and kielbasa to serving plates. Garnish with freshly chopped parsley or green onions and serve warm alongside sour cream or sauerkraut.