Preheat the oven to 170° C fan / gas mark 5.

Line two baking trays with baking parchment.

Prepare a piping bag with a round tip (about 1 cm wide).

In a mixing bowl, sift together the plain flour and the baking powder and set aside.

Separate the eggs and whisk the egg whites until they form peaks. Set these aside.

Add together the egg yolks and 30 g Splenda and whisk together until light and fluffy (about 5 minutes).

Gently fold into the egg yolk mixture the egg whites. When combined (it might take a couple of minutes), gently add the flour mixture and fold through until combined.

Place the mixture into the piping bag and pipe biscuits onto the trays (about 5 cm long).

Bake in the oven for 15 minutes or until golden brown. Leave the biscuits to cool.

While the sugar-free sponge fingers are cooling, whisk together the Quark, creme fraiche, 2 tablespoons Splenda and vanilla extract until smooth and creamy. Place in a bowl and pop in the fridge.

Make your espresso and make sure it is cooling, ready in a bowl to dip the sugar-free sponge fingers into.

Dip the sugar-free sponge fingers on both sides into the coffee (the length of time depends on how strong you like the coffee flavour to be) and arrange them on the bottom of a lasagne dish or trifle bowl. You can also arrange the layers into individual bowls or glasses, depending on how you wish to serve them.

Spread about 1/3 of the creamy filling on top. Repeat two more times, ending up with a layer of cream on top.

Wrap the lasagne dish with plastic wrap and refrigerate for at least 4 hours or preferably overnight.

Dust with cocoa on top just before serving.