1. Add the milk, butter, brown sugar, and lemon zest to a small pot and bring to a boil. Remove from the heat and stir in the poppy seed. Set aside and let soak for a while.

 

2. Preheat the oven to 340°F (170°C). Line a 9.5 inches (24cm) springform tin with baking parchment and set aside.

 

3. Divide the eggs. Add the butter and egg yolks to a large bowl and mix until light and fluffy. Slowly add the sugar and mix in well. Add the lemon zest, lemon juice, and vanilla extract and mix in. Mix the flour with cornstarch, and baking powder and sift into the bowl. Mix until well combined. Add the curd cheese (quark), cream cheese, and sour cream and mix in. Add the egg whites with a pinch of salt to a second bowl and whisk until stiff peaks form. Add the stiff egg whites to the bowl and carefully fold in – you want to keep as much volume as possible.

 

4. Add about 2-3 tablespoons of the cheesecake filling to the pot with the poppy seed filling and mix to combine. Fill into a piping bag with a large round tip. Add the remaining cheesecake filling to the prepared springform and smooth out the top. Pipe the poppy seed filling in several spots into the cheesecake filling and bake for 45-50 minutes. You want to keep the cheesecake pale, some color is fine, but if it gets too dark, cover with some baking parchment and keep baking. When the sides of the cake are firm, but the center is still wiggly, take out of the oven and let cool down on a wire rack. When cooled completely place in the fridge and cool for at least 3 hours, better overnight. Serve with some fresh berries or fruits.