Try this keto version of sernik: the most loved Polish dessert. It's made with creamy twaróg – Polish farmer's cheese, and it has a delicate taste and heavenly aroma!
Separate the eggs, and keep the whites in the fridge until its time to beat them. Keep the yolks out, so they are not cold when mixing into the butter.
Butter a 7" x 3" pan, and line the bottom of the pan with a disc of parchment paper. Butter the parchment paper, too.
Use the paddle attachment of the stand mixer (or the regular whisks if using a hand mixer) to beat the butter on medium speed until soft and pale.
Slowly add the powdered sweetener to the butter, creaming them together until light and fluffy. Use a spatula to scrape the sides and bring the mixture to the center as needed.
Add the egg yolks one by one, alternating with the whey and coconut flour, while the mixer is running. Add the cheese, half at a time, and continue beating on medium speed.
When the cheese mixture is lump free, add all the spices and extracts, including the bergamot zest. Beat for another minute or so, on higher speed.
Retrieve the egg whites from the fridge, and beat them to stiff peaks.
Add half of the stiff egg whites to the top of the cheese mixture. Using a large whisk, by hand, gently incorporate the whites into the cheese mixture, in circular movements starting from the top, gradually going deeper.
Add the remaining egg whites and gently fold them in with a spatula. The mixture should be really thick and creamy.
Pour the batter into the buttered pan, and use the spatula to make the surface level.
Bake the sernik in the pre-heated oven at 170 °C (340° F) for about 1 hour to 1 hour 15 minutes - until the top is golden and the edges are just browned. The center should be near set - just a slight jiggle when tapped. (Not wobbly like an American style cheesecake).
Turn off the oven and open the door slightly, and leave it inside to slowly cool it down. Unmold after it reaches room temperature.
Notes
This cheesecake is not as sweet as American cheesecake. It's a delicate mix of tart (from the Polish farmer's cheese) and warmth from the spices. If you prefer a sweeter cheesecake, just add more sweetener, 50% more should be enough.The cheesecake will grow a lot in the oven, and it might crack a bit (the potato starch used in the traditional recipes helps prevent cracking). After cooling down, it will flatten somewhat, so the cracks won't be as noticeable. If this happens and they bother you, you can sprinkle powdered sweetener on top.