Instructions

Preheat oven to 375°F. if baking immediately. 
Defrost spinach in microwave ( about 7-10 minutes on high )
Place in strainer and squeeze to remove as much water as possible, coarsely chop.

Melt two tablespoons butter (or heat oil ) in a large heavy skillet over moderate heat, add onions and saute for a minute till softened, then add spinach, dill and flour, cook an additional 4 minutes.
Remove from heat, Season with salt and pepper to taste ( and add Parmesan and other optional seasonings if using ) . Let filling cool.
Using fork, whip eggs and add crumbled ( or chopped ) feta, nutmeg and lemon juice.
Melt stick of butter in a small saucepan ( or melt in bowl in microwave ) then cool.
Cover phyllo stack with 2 overlapping sheets of plastic wrap and then a dampened kitchen towel.
Take one phyllo sheet from stack and arrange on a work surface with a long side nearest you (keeping remaining sheets covered) and brush with some butter. Top with two more and brush each with butter. Cut buttered phyllo stack lengthwise into 4 strips ( 4 long thin strips ).

( Optional: place filling on cutting board, shape to rectangle and divide into 48 squares ) 

Put a heaping teaspoon ( or on square ) of filling near one corner of a strip on end nearest you, then fold corner of phyllo over to enclose filling and form a triangle. Continue folding strip (like a flag), maintaining triangle shape. Put triangle, seam side down, on a large baking sheet and brush top with butter. Make more triangles in same manner, using all of phyllo.

Bake triangles in middle of oven until golden brown, 20 to 25 minutes, then transfer to a rack to cool slightly.