Pre heat the oven to 180°C.
Spray a 24 cup silicone muffin tray with a little low calorie cooking spray.
Put the eggs and granulated sweetener into a clean bowl and whisk until the 'ribbon stage' is reached. This is when the mixture has thickened so that when you lift the whisk out it leaves a trail on the surface for a couple of seconds. You should probably use an electric whisk for this!
Fold in the sifted flour and 1 tsp of vanilla extract.
Divide the sponge mix equally between the 24 cups. You should get around ½ a tbsp of the batter in each muffin cup.
Bake for 7-8 minutes, until the sponges are a light golden colour. Remove from the oven and allow to cool.
Using a small knife or a small melon baller, remove a small ball from the the middle of each cake.
Spoon ½ tsp of lemon curd into the wells in the centre of each cake.
Add the sweetened quark to a bowl and stir in the remaining 1/2 tsp of vanilla extract. Pour into a piping bag fitted with a small star nozzle and pipe a small swirl over the top of each cake to cover the lemon curd.
Dust with a little cocoa powder or drinking chocolate if you want or sprinkle with a crushed up Flake.
Allow to cool slightly, and then mix in the quark/fromage frais, whisking until smooth