1. Line a 10 inches (26cm) springform tin with baking parchment and grease lightly. Set aside.

 

2. Add the flour for the base together with the sugar and baking powder to a large bowl and mix until well combined. Add the cold butter in small pieces, mix with the flour and cut into pea-sized pieces with a pastry blender or knife. Add the egg and mix/knead quickly until you get a smooth dough. Roll out the dough on a floured surface slightly larger than the tin. Place in the prepared tin and press to the bottom and sides to form a nice crust (almost up to the edge). If the dough is too crumbly cut a circle in the size of the tin and place inside the tin, use the rest of the dough to make a long sausage and press that to the sides of the tin to shape the sides of the cake crust. Place in the fridge for about 30 minutes to cool down.

 

3. Preheat the oven to 350°F (180°C). Wash, dry and pit the mirabelles. Set aside. For the streusel add the flour, sugar, butter, and vanilla extract to a bowl and mix with your fingers until nice and chunky streusel form. Place as well in the fridge to cool down.

 

4. For the filling mix the low-fat curd with sour cream, sugar, cornstarch, eggs, and vanilla extract until smooth. Add the poppy seed filling and mix in. Pour that filling into the prepared cake crust, top with the mirabelles and sprinkle with the streusel. Bake for 40-45 minutes until the streusel have a nice golden color. Take out of the oven and let cool down completely in the springform tin. When cooled, place at least 2 hours in the fridge. Before you cut the cake, let it come to room temperature again. Serve with some whipped cream.