If you are starting from scratch and don't have a couple of cups of spanakopita filling left from a different dish then prep your spinach by making sure you have squeezed out as much of the water...this is very important. I use a cheese cloth or thin kitchen towel to twist the water out.
Sautee the white and light green parts of the chopped green onions in about a teaspoon of olive oil, set aside.
Mix the first 10 ingredients together (from spinach to egg) well (you will add the sautéed green onions and the darker greens at this time), this is your basic spanakopita filling. If you have your own version of filling left over than use that instead, you will need two packed cups worth, and continue with step 4.
Add in the cream cheese until well incorporated.
Mix the shredded cheese with the grated cheese to combine and reserve 3/4 cup for topping.
Add in the rest of the cheese and red pepper flakes to the spinach mixture and combine well.
Add mixture into an oven proof dish brushed with a light layer of olive oil.
Evenly top with reserved cheese and bake at 350 degrees Fahrenheit for 25 minutes, or until it starts to lightly bubbly on the sides. If you want the cheese to have a light brown color broil for the last 1 to 2 minutes, but keep an eye on it.