In a food processor (or mixer) crush your Oreo biscuits to a fine powder and remove in a bowl. Mix the ghee in, very well and evenly, using your fingers
Empty this mixture in the centre of your tart tin and spread it around to cover it evenly. Keep this in the refrigerator to chill for at least 15 minutes
Mix the gelatin with equal quantity of hot water and set aside
In a mixing bowl, add the Greek yoghurt, mango pulp and the gelatin and whisk very well. The gelatin needs to gel in uniformly
Remove the tart shell out of the refrigerator and pour the yoghurt mixture (aamrakhand) in it. Again put it back to chill for at least an hour or two
When well set, remove your yummy Oreo mango shrikhand tart from the fridge, slice it up, garnish with some chopped fresh mangoes, nuts and mint leaves and serve. Enjoy!