Mix feta, ricotta and egg together. In a 9x13 inch pan, layer 4 sheets of phyllo dough brushing butter between each layer. spread 1/3 cheese mixture and continue layering phyllo and cheese mixture (like lasagna) until cheese mixture is gone. place a final layer of phyllo dough on top and lightly score the top layer along the lines that you intend to cut. Bake banitsa at 375 degrees for 40-45 minutes until golden brown. Let cool for 10 minutes and then cut while warm.