In a bowl, mix the egg yolks with the fine semolina. In a saucepan, add the creme fraiche, milk, rosewater, orange zest and vanilla, and bring a little before to a boil. Gradually pour the hot crème fraiche and milk mixture on top the semolina mixture, stirring with a whisk. Add the flour. Return the mixture to the saucepan and cook, stirring, until it bubbles, and add the pistachios. Remove it from the fire. In a 34cm baking pan, butter half the sheets and pour the mixture on top; add the remaining sheets, after buttering them. Bake in a preheated oven at 160°C, for approx. 35-40 min.