Preheat the oven to 180°C convection oven. Mix the flour, sugar, baking powder, cacao and vanilla sugar in a bowl. Add the rapeseed oil and sparkling water to the bowl and mix briefly (!) with a whisk to form a batter.
Grease a 15x20cm, at least 5 cm deep baking dish with margarine.
Pour in the batter, smooth down and bake on the middle shelf of the oven for 20 minutes. Use a toothpick to test whether the cake mixture is cooked through. To do this, simply prick in the middle of the dough.
If no cake mixture sticks to the toothpick, the cake is done. Remove the chocolate cake from the oven and let it cool down on a rack.
Meanwhile, peel the orange very thinly with a knife and cut the peel into strips as fine as possible. Bring the sugar to the boil with 100 ml water. Boil down the orange peel with the sugar water until the syrup starts to thicken. Remove the orange peels from the syrup and leave to dry on a rack.
Cut the chocolate base into oblong rectangles, halve each horizontally. Spoon ½ tsp. orange marmalade on the bottoms of the halved cake bars, place the other half on top, chill for 20 minutes.
Roughly chop 2 bars of Lovechock Winter Spice Mandarin and slowly melt over a bain-marie. Dip the cake bars into the liquid chocolate. Decorate with the candied orange peel and leave to cool.

Tip: The glaze will be especially nice and crisp if you repeat the "dipping" process once and let the bars cool in between.