Preheat the oven to 200C/180 Fan/Gas 6.

Cut 2 pieces of baking paper to fit 2 shallow baking trays approximately 32 x 22 cm.

Roughly chop the cooked beetroot and put it into a food processor with a splash of water.

Process until very finely chopped or completely pureed, depending on your preference.

Measure out 100ml of the mixture: top up with water if you don't have 100ml.

Put the flours, nigella seeds, salt, olive oil and the 100ml of beetroot mixture into a bowl.

Using a plastic spatula, bring everything together into a soft dough. Add a little more water if needed, but don't make the dough too wet.

Put one of the pieces of baking paper on the worksurface and dust with a little flour.

Cut the dough in half: put one half on the dusted baking paper and cover the other half with the upturned bowl to prevent it drying out.

Lightly dust a rolling pin and the dough, then roll it thinly so it fits the approximate shape of the paper.

Tip: if you don't want the beetroot to stain your rolling pin, cover the dough with another piece of baking paper before rolling out.

Use a ruler and a pizza wheel or knife to cut off excess dough so that the edges are straight (add scraps to the dough half you reserved).

Cut the dough into squares or rectangles of your chosen size (be careful not to cut through the paper).

Slide the baking paper and crackers onto a baking tray.

Put in the preheat oven and bake until cooked through and crispy (18-25 minutes)

Tip 1: Crackers at the edges of the tray may cook more quickly, so remove them before they burn.

Tip 2: As the dough is moist due to the beetroot, you may need to turn the crackers over part way through to ensure they're dry and crisp throughout.

While the crackers are baking, repeat the process with the remaining dough.

Transfer the crackers to a wire rack and leave until completely cold before storing in an airtight container.

Beetroot Crackers should keep fresh for at least 2 weeks.