Fill a pot with a generous amount of water and bring to a boil.
Add the mandarins and boil for 30-40 minutes, making sure that they are always completely submerged in water while boiling. Add more water if necessary.
When ready, remove the mandarins from heat, drain and allow to cool.
Cut them in half, squeeze them thoroughly and discard the pulp and any seeds.
Transfer the remaining parts of the mandarins to a food processor and beat until pureed. Set aside until needed.
Place a non-stick pot over medium heat. Add the oil and let it get a little hot.
Add the coarse and fine semolina and sauté carefully. Do not let the mixture burn. Mix continuously with a wooden spoon because it burns quite easily.
Add the water, sugar and mandarin pureed. Mix and cook for about 10 minutes until the mixture thickens.
As soon as you see bubbles forming in the mixture, your halvah is almost ready. Continue mixing. (If you think it may burn, lower heat). You will know it is ready when it pulls away from the bottom of the pan on its own, when you tilt the pan sideways.
Divide the mixture in half. Transfer half to a bowl and leave the other half in the pot.
Finely chop the couverture and add it to the mixture in the pot. Mix with a wooden spoon. The chocolate will melt completely since the mixture is still hot. Mix until the mixture is completely chocolatey brown.
To the other half in the bowl, add the orange zest and mix well.
Transfer the brown mixture from the pot to a 23 cm cake pan with a hole in the center. Press down on it all the way around with a spoon to make it compact and even on the surface.
Add the remaining mixture over it and press down again with a spoon to make it compact and even.
Set it aside to cool for 30-40 minutes at room temperature and remove from pan.