In a 10-inch cast iron pan set over medium heat, warm up one tablespoon of olive oil. Sauté the leek, onion, and scallions for one to two minutes, or until they become slightly clear.
Clean your pan after it has cooled down, or just quickly wipe it down with a paper towel. Put the pan on low heat and add two tablespoons of olive oil.
Make sure the bottom is fully covered. Put the egg mixture for the frittata into the pan and cook for 8 to 10 minutes, or until the sides start to set.
Add the frittata to a medium oven shelf and broil on top. Check every few minutes to prevent the top from browning for 8–10 minutes.
Turn off the grill and let the frittata finish cooking in the oven if the top cooks faster than the inside. Offer the quiche with extra herbs on top.