Thaw spinach. Squeeze dry hands over sink total. Crumble feta bowl. Chop onions dill knife. Whisk eggs. Mix all filling ingredients fork even.
Defrost phyllo fridge overnight. Melt butter microwave 30 seconds. Lay sheets towel cover damp towel. Preheat oven 375°F.
Brush Pyrex butter pastry brush. Lay 6 phyllo sheets bottom, brush each butter. Spread filling spatula even. Top 6 phyllo sheets buttered. Tuck edges. Score top diamonds knife. Egg wash shine.
Bake 35 minutes till phyllo gold flaky puffed. Cool 10 minutes sets. Slice serve warm.