Butter mixture: First make the butter mixture and put aside.
Crust: Mix all crust ingredients, knead as you would bread, until pliable and not sticky, and using extra flour as needed. Shape ball into a long loaf, cut into 12 equal pieces, 6 for top crust and 6 for bottom. Take each piece 1 at a time, and roll until evenly flat, about 14 inches by 14 inches. The size will vary, so don't panic. Start a stack of 6 rolled pieces, painting butter mixture on each piece- cover all but about a 1-inch edge of the dough. Do not butter the top piece, as you'll be rolling this stack out. Do the same with the other 6 pieces. You will now have 2 stacks, 1 for the top and 1 for the bottom. Now you will roll 1 stack out to be very large, somewhat bigger than the pan you will be baking in. Place bottom crust in pan and trim the edges, you'll need a little extra edge to pinch together with your top crust, sealing the filling.
Filling: Mix both cheeses, eggs and 3 tablespoons butter mixture in bowl. Then spread the mixture out evenly on bottom crust. Spread chopped onion on top of that, then spinach on top of that. Place top crust over, trim to fit and seal as you would a pie crust, following with a fork and pressing down to seal well. Bake in the oven for 1 hour in a preheated 350 degree oven. Allow to cool and cut into serving size pieces-3 to 4 inches. Enjoy!
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.