To make the dough, combine flour, sugar, baking powder, and salt in a bowl. Using a pastry blender or two knives cut the butter into the flour mixture leaving a coarse and crumbly texture (mixture will contain some lumps).
In a separate bowl, beat egg yolks into the sour cream. Stir the beaten egg yolks into the dough mixture. Knead in the bowl until mixture begins to form a dough and is well mixed. Wrap dough in plastic wrap and refrigerate one to two hours.
Roll dough out on a lightly floured surface to fit a 13 x 9 x 2" pan in approximately I 15 x 11" rectangle.
Line the bottom of the pan with the dough, stretching to fit so that it comes up to about two thirds of the way up the sides of the pan.
For the filling, beat the eggs and egg white at high speed of electric mixer until thick. Add the sugar gradually, continuing to beat at high speed until egg whites are stiff, but not dry, and peaks form.
Press the cheese through a sieve or potato ricer or pulse in food processor. Fold gently into beaten egg white mixture.
Add the remaining ingredients. Mix thoroughly, but gently so as not to deflate the egg whites.
Turn the cheese filling into the dough lined pan.
Bake at 350F for 40 minutes or until set.
Cool and cut into squares.
Submitted by: CM
