If you intend to use the dough straight away, heat the oven to 160°C

Mix all the ingredients (except those for brushing and topping) in a bowl and work the butter into the flour mixture. Keep working the doughmixture until it is all blended and forms a firm dough. If needed, adjust the thickness with a few drops of water if required or add a little flour if too sticky.

You can leave the dough a few hours for the sourdough to work some more in developing the flavour, or you can use straight away.

Sprinkle rye flour on the work surface, put the dough in the centre and sprinkle a little flour on top. Roll out the dough as thinly as possible. Cut into 10cm strips and then roll again from the short edge lengthways and then the biscuit dough will roll even thinner. Tidy up the edges with a cutter to make an oblong – you can use either a metal scraper or a pizza wheel. Cut the dough into 5cm x 10 cm strips. In practice you will probably make various size oblongs and this works fine too

You can bring all the off cuts together and reform. If the mixture is too dry then add a sprinkle of water and mix into the dough and re-roll.

The quantity here will fill 1 baking tray. Lay the dough strips on the tray and prick the surface with a fork. Brush the crackers with oil and grind the black pepper over the top.

Bake at 160°C for 12 minutes. Baking time does depend on the thickness of the rolled out dough and could take 4 or 5 minutes more. The biscuit will not be crisp until it cools down. Place the warm biscuits on a cooling rack and allow to cool. If when cooled, they are not crispy then heat the over to 140°C and put the biscuits back in the over on a tray for a further 5 or 6 minutes.