Wash and peel the carrots.
Cut in roundels and transfer to a bowl, add a cup of water and pressure cook in the cooker for 2 whistles.
Let the pressure drop naturally. Remove the carrots and cool them completely.
Meanwhile, peel the oranges remove the segments slit open, discard the membrane and seeds. Better to do this in a wide bowl this way the orange juice is collected too.
To a blender/mixer, add the carrots, sugar and the water that you have used to boil the carrots.
Blitz till the sugar is well mixed and all the ingredients are well crushed.
Adjust the sugar, add the lemon then add water as needed. The amount of water you need will depend on the orange juice you have.
Transfer to a flat container and set in the freezer till the juice freezes.
Actually, you have to remove from the freezer and use a fork to scrape and stir the granita. Transfer back to the freezer. Do this at least 2 times. I did not I just scooped the granite and shaped it into these cute balls.