Preheat the oven to 180° C w/ fan.
Put all ingredients for the pastry in a bowl & knead together w/ your hands.
Form a ball & roll out the pastry between sheets of cling film. Remove the cling film & put the pastry in the tart form. Adjust the pastry to the tart form.
Let it prebake for about 20 min.
In the meantime prepare the orange zest & grate the chocolate.
In a bowl whisk together the ricotta, the icing sugar & the eggs.
Add orange zest, grated choclate & minced pistachios.
As soon as the prebaking is finished reduce the heat in the oven to 160° C.
As soon as the pastry has cooled down - about 10 min - pour the filling into the pastry. Sprinkle w/ the rest of the pistachios.
Bake in the oven for about 35 min.