Melt the brewer’s yeast with some lukewarm water in a bowl with the sugar and let it rest for 15 minutes.
Mix the flour, the sugar and the cubed butter in a bowl then pour the melted yeast in the centre, together with the rose water and the pistachios. Knead the mixture well for about 10 minutes on a table, then leave to rest for about 2 hours at room temperature.
With small quantities of pastry, form small cylinders then cut them in small pieces of about half centimetre.  Press the thumb on the pieces, arranged on a plate with sesame seeds, to give them the shape of rose petals. Cook in the pre-heated oven (180 C) for about 10-15 minutes.