Traditional Polish Christmas treat. Known in Germany, Poland, and further East with only small variations.
Based on slightly drier version of farmer's cheese called quark (twaróg), this semi-sweet, moist, and fulfilling cheesecake will tear down the preconceptions you have about cheesecake in general.
Salty butter and the potato add a robust base to the lightness of the beaten egg whites.
Find your own balance by adjusting the amount of sugar and vanilla. Aim for slightly under-sweetned cake mix and let the raisins and candied orange peel to pull the sugary weight. It's subtle and takes some practice. Below numbers are just a starting point that should result in an acceptable first try.
Chop peel of two large oranges into 3-5mm cubes, soak in water 24h. Change water mid-way.
Boil in sugary water until very sticky and almost dry. It should taste like candy.
Pour boiling water over the raisins/sultanas to cover. Leave to soak for a few hours until soft and juicy. Drain and sift a small amount of flour through them so they don't stick.
Run the quark twice through a food processor or a mincer. The goal is a fine texture without the typical lumpiness of quark (twaróg).
Boil the potato, skin on, until soft throughout. Put to one side to cool well. Peel and mash it as well as possible with a fork or a potato masher.
Set oven to 80C.
Prep a 25cm squared, deep baking tray by rubbing a block of butter all over the insides and once covered coat them evenly with breadcrumbs. They should stick while sloshing them about the baking tray. Pour out the excess breadcrumbs.
Pour the cake mix into the tray.
Put tray in the 80C oven for 5 minutes and then increase the temperature to 180C.
Bake for around an hour. The surface may crack, that's fine. If your oven doesn't heat evenly, turn it around every 30 minutes or so for even bake.
After an hour, probe with a wooden skewer all the way in. If it comes out wet and/or sticky, add another 15 minutes and re-test.
Repeat until the skewer probe comes out dry.
Take the cheesecake out of the oven and leave to cool for at least 3 hours. Best overnight, covered.
Can be served topped with icing sugar, fresh forest fruit, whipped cream. Get creative. It's a good base. Perfect on its own.