Finely dice onion, place it in to a large skillet with 2 tbsp oil and saute on med-high heat until golden.
Add 2 boiled, diced eggs along with 2 cups of cooked buckwheat. Mix it well and remove from the stove. Feel free to add some salt if desired. It should be warm, not hot. This is your filling.
In a mixing bowl combine 6 cups (2 lbs) of mashed potatoes with 1 raw egg and mix it in. Add 2 cups of flour and mix well. Your mixture should not have lumps of flour.
Use an ice cream scoop to get even portions of dough. Scoop out balls of dough and flatten them into patties (keep your hands floured, to prevent the dough from sticking).
Place 1 tbsp of buckwheat filling in the center of each patty, fold patty to close and seal the edges with your fingers. Mold it into the shape of a pancake. Try to flatten the sides for more even cooking.
Preheat 1 or 2 skillets, fill them with enough oil to cover the bottom. Cook pancakes until golden brown on each side over medium heat (about 4-6 minutes per side). If Your pancakes are browning too quickly, turn down the heat.