In a medium pan, over medium heat warm 1 tbsp olive oil. Sauté the onion until soft for about 5-7 minutes. Set aside.
Wash the potatoes and place them in a pot (whole with the skin on), add cold water covering the potatoes by about an inch, add a bit of salt, boil them until they can be pierced with a fork for about 20 minutes (it may take a bit longer for larger potatoes. Drain, run cold water over them and cool until you can handle them, then twist the potato and the skin comes right off. Or place the potatoes in an ice bath for a few seconds and peel.
Preheat oven at 400 F (200 C).
Mash the potatoes with a potato masher or food mill. Place mashed potatoes in a large bowl.
Lightly beat the eggs and add to the potatoes. Add the onion, cheese, herbs, salt and pepper. Mix well.
Coat the baking dish with some olive oil and empty potato mixture in the dish. Spread evenly. Make triangle shapes with a fork. *I used a 8 X 12 inch (30 X 22 cm dish).
Drizzle 2 tablespoons olive oil over casserole.
Bake in the oven until golden for about 50 minutes to an hour.
Let it cool for at least 30 minutes before slicing.