preheat the oven to 180 degrees celsius temperature.
grease a cake tin with butter or oil and line with baking paper, allowing two sides to overhang.
sift the flour and baking powder together.
chopped the butter and place the butter and sugar in a bowl.
beat the butter and sugar with an electric beater until creamy.
add the flour and beat until a soft dough forms.
transfer to the prepared tin and use floured fingers to press firmly into the tin.
bake for 15-18 minutes or until golden and firm to touch.
set aside to cool completely.
for the jelly, combine the orange juice and sugar in a saucepan.
stir over medium heat until the sugar has dissolved.
sprinkle the gelatin powder evenly over the top of that orange juice. **can melt the gelatin powder separately with little bit of medium hot water and then mix with orange juice**.
remove from heat and stir until the gelatin is dissolved completely and get a lump free mixture.
place in the fridge and stir occasionally, until jelly is getting thick and nearly set.
slowly pour the mixture over the cake base.
place in the fridge for 2-3 hours or until the jelly is set.
for the chocolate ganache, break the dark chocolate and place in a heatproof bowl.
heat the cream in a small saucepan over medium high heat until just simmering.
pour the cream over the chocolate.
when the chocolate starts to melt stir until smooth and glossy.
Set aside for few minutes to thicken slightly.
Remove the jelly from the fridge.
carefully spoon the chocolate mixture over the jelly.
place in the fridge for 2-3 hours or until set.
use the hanging baking paper to lift the slice out of the tin.
Cut into squares. **to get a perfect cutting, use a slightly hot knife.**