Wash, peel and chop the beetroot.
Using a blender, blend the beetroot with a little water at first to a smooth puree. Then add the remaining water and blend.
Run it through a sieve to catch the pulp and re-blend any large bits.
Add sugar to the beetroot juice.
Boil over medium heat. Stir until sugar is blended well.
Continue cooking until the raw smell disappears. Keep skimming the foam that is formed on the top.
Once it becomes thick, remove from heat and let it cool down.
Boil the milk in a heavy-bottomed non-stick pot. Stir occasionally.
Keep boiling until the milk has reduced to half of its original quantity.
Then stir in the beet syrup. Mix it well. Turn the heat off.
Now let the milk cool down till it is just lukewarm.
Take curd or yoghurt, it should be homemade, beat it with a whisk. Add it to the warm milk. Then add strawberry/vanilla essence (optional). Stir well.
Then pour it into the desired pot or container. A clay pot is the best but if you don't have that then you can even use a glass bowl. Cover with foil and allow it to set in a warm place for 10 to 12 hours. Don't disturb it, as it can ruin the shape.
Once it sets completely, keep it in the refrigerator for 2 to 3 hours. Then serve the chilled mishti doi.