The onions are finely minced; yielding about 2½ cups. The parsley is cleaned in our salad spinner [howto:salad] and then the leaves are chopped. We have ½ cup of chopped parsley.
We clean the spinach in batches—a sixth at a time. We do not spin it in our salad spinner too much – it is not necessary that it be completely dry. When one batch of spinach is clean and mostly dry, we put it in our empty Dutch oven and begin heating over medium-low heat. We continue to add spinach as it is washed and lightly spun dry as we turn the spinach in the pan with tongs. Spinach that is wilted is removed to a large bowl.
When all the spinach is added to the Dutch oven, there is still half of the original quantity that is not wilted. At this time, we cover the pan and cook for a couple of minutes. We remove the cooked spinach to a clean bowl and discard the liquid in the pan.
While the spinach cools, we heat 3 tablespoons of the extra-virgin olive oil in the Dutch oven over medium-low heat and add the minced onion. We cover and cook for 5 minutes. While the onion sweats, we use our “ricer” to squeeze the excess water out of the spinach. In small amounts, we add spinach to the ricer with tongs and squeeze the liquid into another bowl. The “dry” spinach is removed from the ricer with tongs and put on a large dinner plate. We continue with the rest of the spinach. We have 2½ cups of spinach on the plate. We use kitchen scissors to coarsely chop the spinach. It already is “baby” spinach so this is a quick step.
After cooking the onion for 5 minutes, we uncover the pan and stir. The onion is soft and still light-colored. We add the chopped spinach, some salt and pepper, grate in 20 scrapings of some nutmeg with the microplane (we are looking for a “pinch”), and the chopped parsley. We stir well and then remove the pan from the heat. We set it aside to cool for a few minutes before stirring in the feta cheese.
At this point we preheat the oven to 350° F. We could also just cover and refrigerate the spinach feta filling now if we wanted to cook the tart later.
In a large measuring cup, we melt the butter in the microwave until it is just melted. We add the remaining olive oil to the measuring cup and stir with a pastry brush.
We have our 9-inch tart pan (with a removable bottom) ready. The phyllo dough package is removed from the refrigerator and unrolled on a clean surface. To help prevent the dough from drying we keep it covered under plastic and a damp paper towel, as we work with a sheet at a time.
First, we brush the bottom of the tart pan with the butter-oil mixture. Then, we brush a phyllo sheet lightly with the mixture, according to the package directions. The sheets are narrow for the tart pan, so we lay the sheet such that it covers 2/3 of the pan and drapes over the edge of the pan. The next sheet (also lightly brushed with oil) we lay on the other side of the pan, overlapping the first sheet and completely covering the pan with dough.
The next coated sheet is spread in the middle of the tart pan. We continue in this manner—buttering each sheet and laying it into the pan—so that the bottom is built up with the phyllo dough and there is an overhang of dough around the circumference of the tart pan. When we have used all but 8 sheets of the phyllo (a bit more than half of the package) we fill the tart.
We give the spinach feta mixture a stir and taste for seasoning. We add a little more salt and pepper and then spread it into the tart pan.
Six of the remaining phyllo sheets are brushed one at a time and spread over the filling in the same manner as the bottom layers. After we roll the overhanging dough from the bottom and top layers up around the tart pan, we push the rolled edge into the side of the pan gently so there is a nice rolled edge to the tart. The remaining two sheets are brushed with the oil-butter mixture, crumpled loosely, and placed on top of the tart. This gives the tart height and decoration. We have just a small amount of butter and oil left in the measuring cup so we pour this over the top of the tart.
The tart is baked in the preheated oven for an hour. We want the crust to brown and the tart filling to be hot.
We put the tart pan directly on the bottom rack in the oven, but it made a small mess in the oven! Next time, we will put in up a rack and lay a sheet pan under the tart to catch any drippings.
When the spinach feta tart is done, we remove it from the oven to cool on a rack for a few minutes. Then we remove it carefully from the tart tin, cut and serve.