Cook potatoes in plenty of salted water until cooked through. Meanwhile gently fry onion until translucent and set aside.
In a large bowl, combine potatoes, eggs, pancetta, onions, butter and chives. Season with salt and pepper to taste. Adjust the texture with a bit of milk if necessary.
Preheat your oven to 400°F (190°C) and line a baking sheet with parchment paper.
On the baking sheet, using a ring mold, sprinkle a layer of breadcrumbs, then scoop potato mixture to shape the cakes—about 1 ½ inch thick. Press down slightly with the back of a spatula and finish with another thin layer of breadcrumbs. Remove the ring mold and repeat the process.
Bake in the oven at 400°F (190°C) for 10 minutes, or until golden, and serve the baked potato cakes warm, with a sprinkle of grated parmesan on top.
