Sernik Polish Cheesecake - cooking recipe

Ingredients

Dough
1 1/2 cups flour
1 teaspoon baking powder
1/3 cup sugar
1/4 teaspoon salt
1/4 cup unsalted butter, chilled
1 egg
1/4 cup sour cream or 1/4 cup plain yogurt
Filling
6 eggs, separated
2 cups sugar
1 teaspoon vanilla extract
6 tablespoons unsalted butter, softened
1 1/2 cups mashed potatoes, unseasoned about 3 medium
1 lb farmer cheese
1/4 cup Grand Marnier or 1/4 cup limoncello
1/2 teaspoon fresh grated nutmeg
1/2 teaspoon salt
1 orange zest or 1 lemon zest

Preparation

Preheat oven to 350 degrees.
Dough:
Pulse flour, baking powder, sugar, and salt in a food processor and butter and pulse till crumbly. Add egg and sour cream mix till it comes to a ball.
With heavy floured hands press into a 13x9x2 pan bring up a touch on the sides of the pan. It will be sticky.
Filling:
Beat egg whites in a mixer till stiff, set aside.
Beat egg yolks, sugar and vanilla till light and creamy.
In a food processor place butter, potatoes, cheese, Grand Marnier or limoncello, nutmeg, salt and zest of lemon or orange pulse till all combined.
Add to yolk mixture folding in to incorporate.
Fold in beaten egg whites.
Pour on to crust.
Bake for 45-50 minutes.
Turn oven off and let cool with door ajar.
Cool well before serving.