Place the flour, salt and egg whites into a large bowl and mix. Add the water a little at a time until you have a smooth dough. Roll the dough out on floured surface to roughly the thickness of a pound coin. Place the dough onto a baking sheet lined with parchment paper.
Place the beetroots in the middle of the dough, then pull the dough up around the beetroots, pressing the dough together to seal them in. Bake at 160*c gas 3 for about 2 hours (this really depends on the size of the beetroots. Larger ones will take 2.5 – 3 hours. Leave the dough to cool before breaking open to retrieve the beetroots.