"In Albanian, this savory spinach pie is called Byrek Mi Spinaq and, with its delicate layers of phyllo dough, spinach, and cream, it's a very popular dish. The pie can also be frozen after it is assembled and thawed before baking."
Combine butter and canola oil in a saucepan and warm over low heat until butter is melted. Stir to combine. Reserve two tablespoons of mixture for the filling.
For the filling: In a large bowl, combine the spinach, onion, egg, sour cream, yogurt, salt, and the 2 tablespoons of the butter-oil mixture, and mix well. Set aside until needed.
Use the remaining butter-oil mixture to prepare the phyllo dough. Brush butter-oil mixture onto a baking sheet and lay down 1 sheet of phyllo. Brush more of the butter-oil mixture on top of the phyllo. Continue to layer 9 more sheets with butter-oil. Spread spinach topping evenly over 10th sheet of phyllo. Top spinach with 10 more sheets of phyllo, brushing butter-oil on each layer. Turn up edges of dough and press to seal.
Bake spinach pie for 45 minutes, until top is golden and risen. Use a knife to check the bottom to make sure it is nice and crispy. Let cool for 15 to 20 minutes. Slice and serve.