Pre-heat oven to 160C (fan)
Mix the seeds in a bowl and grate in the Parmesan. Add the water until you have sticky (but not wet) consistency. Turn the mixture out onto a layer of baking paper. Cover with another layer of baking paper and use a rolling pin until about 1/2 cm thick. Remove the top layer of paper. Gently slide the bottom layer with the mixture on it onto your oven shelf (or a large baking sheet).
Bake for 30-45minutes (depending on how thick you have rolled your mixture) until just crispy. Keep an eye on then every 10minutes as they can burn easily.
Allow to cool and store in an airtight container.