1. First thaw frozen spinach by running under hot water in a colander for a bit then squeeze all of the water possible out if spinach and transfer to a skillet pan with olive oil and very lightly saute just to get it warm. If you are using fresh spinach also lightly saute with olive oil.
2. Next finely chop the Vidallia onion or the spring onion and also saute with olive oil in another skillet. Make sure to saute the onion a bit longer than the spinach.
3. Finely chop the bunch of dill.
4. Place the spinach, onion, and dill in a large mixing bowl.
5. Add the 4 blocks of feta and the 6 eggs and begin to mix until the feta is crumbled and evenly dispersed through and the egg has mixed in and you don't see any yolk anymore.
6. Add a dash of pepper
7. Preheat oven to 350
8. Next place a 15 by 10 by 2 inch Pyrex on the a table or counter top and roll out the phyllo dough next to it. Make sure the phyllo dough is still slightly cold from the refrigerator but not frozen and not exactly room temperature because it will tear and stick if too cold and break and become brittle if too dry. It's very sensitive.
9. Melt the stick and half of butter on stove top.
10. Place 2 sheets of phyllo dough in the Pyrex and brush with the butter to cover the entire surface. Then place 2 more sheets of phyllo dough in Pyrex and brush with butter to cover entire surface again. Repeat this process until you have used 3/4 of the roll.
11. Next spoon the spinach mixture on top of the phyllo and evenly distribute across the Pyrex until finished.
12. Repeat laying and buttering 2 sheets at a time of the phyllo until the have finished one pack of phyllo and used about 1/4 or so of another packet. You can eye ball this really and see if the top layer needs more phyllo or not. Doesn't have to be equally thick on top and bottom.
13. Whatever butter is left over pour over top of completed product.
14. With a perforated knife lightly cut through the spanakopita sectioning it into pieces. The phyllo dough is very fragile and will want to tear so be careful. You have to do this before cooking otherwise all of the phyllo will flake off when trying to cut it after it has been baked. You can cut about 20 pieces.
15. Place Pyrex in the oven and back for 45 minutes to an hour. Rotate once half way through. You'll be able to tell when it's ready by looking at the upper layers of phyllo dough. When they are lightly golden brown it is ready. Turn off the oven and let it sit in the oven for another 15 minutes. Then take it out and let it cool for another 15.