Using a peeler peel the parsnip into thin strips and place in a mixing bowl. You might need to discard the woody centre of the parsnip depending on how old your parsnip is. Pat dry with kitchen towel.
Add 2 tbsp olive oil, 1/2 tsp ground cumin and a little sea salt (if using) to the mixing bowl and mix well with your hands rubbing the oil into the parsnip.
Spread out thinly on the greased baking trays. Bake for 15 minutes, turn over with a spatula, then return to the oven for a further 15 minutes. If they don't look crispy (remember ovens vary!) return them for a further 10 minutes. The edges should be turning golden brown.
Remove from the oven and leave to cool completely on the tray.
You can store these for a few days in an airtight container but I have found that they lose their crispness so they're best eaten straight away.