Heat oven to 180C/160C fan/gas 4. Line two baking sheets with baking parchment. Put the flour, baking powder, sugar, 1 tsp salt and a grinding of black pepper in a large bowl, then mix well. Stir in the eggs until the mixture forms clumps, then bring together with your hands into a dough. It will seem dry at first, but keep kneading until no floury patches remain. Add the olives, thyme and parmesan, kneading until they are well distributed.
Tip the dough out onto a lightly floured surface and divide into four pieces. With lightly floured hands, roll each into a sausage about 30cm long. Place two on each tray, well spaced apart. Put in the oven for 25-30 mins until the dough has risen and spread (it should still be pale). Remove, then cool on a wire rack for a few mins and turn down the oven to 140C/120C fan/gas 1.
Cut into slices about 1cm thick on a sharp diagonal, then lay the slices flat on the baking sheets. Bake for 20 mins more, turn over, then bake for another 20 mins until dry and lightly golden. Transfer to a wire rack to cool completely. Will keep in an airtight tin for up to one month.