Heat the oven to 180C (160C fan)/350F/gas mark 4. Put the semolina, flour, sugar and butter in a large bowl with an eighth of a teaspoon of salt. Using the tips of your fingers, rub the mixture to a breadcrumb consistency. Add the vanilla, lemon juice and a teaspoon of water, mix into a pliable dough and set aside.
Put the pecans, sesame seeds, dates, fennel, lemon zest and orange juice in a food processor and blitz to a thick, almost smooth paste.
Put the dough between two sheets of baking paper, then roll it out into a roughly 34cm x 22cm rectangle that’s about 3mm thick. Using a spatula, carefully spread the date paste evenly over the dough, then, using the paper to help you, roll it into a log about 6-7cm in diameter.
Brush the top of the log with a little water, scatter on the remaining sesame seeds and use the paper to press the seeds into the top of the dough. Cut the log at an angle into 2cm-thick slices.
Arrange the slices seam side down on a lined baking sheet and with sesame-studded side facing up. Bake for 20-25 minutes, , rotating the cookies once halfway, until slightly golden on top, then remove and leave to cool.