Begin by peeling and dicing your Russet or Yukon Gold potatoes into equal-sized chunks. Place them in a large pot of cold salted water, bringing it to a boil over medium-high heat. Allow the potatoes to simmer for about 15–20 minutes until they are fork-tender. Drain the potatoes thoroughly and mash them until smooth and creamy.

In a skillet over medium heat, add a small amount of butter or oil and toss in the finely chopped onions. Sauté for about 5–7 minutes, stirring occasionally until the onions become transparent and sweetly fragrant. Remove from heat and set aside.

In a large mixing bowl, combine the warm mashed potatoes with the sautéed onions, eggs, chopped pancetta, remaining butter, and fresh chives. Season with salt and pepper, adjusting to taste. Stir everything together until well blended.

Preheat your oven to 400°F (190°C). Shape the potato mixture into uniform cakes, approximately 3 inches wide and 1 inch thick. Sprinkle each cake lightly with breadcrumbs on top.

Carefully slide the baking sheet into the preheated oven and bake for about 10–15 minutes until golden brown on the edges.

Plate your deliciously golden Oven Baked Mashed Potato Cakes while warm. Serve with grated Parmesan cheese or sour cream on the side.