1. Combine all ingredients for dough and knead until smooth.
2. For the filling, beat egg whites until stiff, add sugar and beat until peaks form. Combine remaining ingredients, fold into egg whites. Mix thoroughly.
3. Divide dough in half. Roll out one part on well-floured surface. Place into 10×16 inch pan. Pour cheese filling over dough. Roll out second half of dough, place over cheese filling. Prick dough with fork. Brush with egg yolk.
4. Bake at 350 degrees Fahrenheit for one hour.