• Preheat oven to 400˚F (200˚C) and grease a 9×13 inch (23×33 centimeter) baking dish with olive oil.
• In a large pan, drizzle the 2 tablespoons (30 milliliters) olive oil over medium heat.
• Add onions and cook, stirring often, until lightly browned.
• Sir in the ground beef, breaking up with a spoon, and season with salt and pepper. Continue cooking and breaking apart the meat until browned. Remove from heat and set aside.
• Peel the potatoes and cut into 1/4 inch (6 millimeter) thick slices.
• Layer half of the sliced potatoes, about 2 layers, across the bottom of the prepared baking dish. Season with salt and pepper.
• Cover the potatoes carefully with the cooked ground meat in an even layer. Top with the remaining potatoes, another 2 layers.

To make the topping:

• In a medium bowl, whisk together the eggs, sour cream or yogurt, milk, salt, and pepper.
• Pour evenly over the potatoes. Bake in the preheated oven until potatoes are tender and top is golden brown, about 45 minutes to 1 hour. Broil, if desired, to crisp the top further.
• Allow to sit for 10-20 minutes to settle before slicing and serving. If desired, sprinkle with a little chopped parsley.