Crush the biscuits in a mixer and add melted butter to it and give one more whizz for the butter to incorporate properly.
Take a 9 " loose bottomed Tart Pan and press the crushed biscuits equally from all sides with your fingers to take the shape of the fluted pan to form the base and sides. Keep it in the fridge for 15 minutes to set and harden.
Meanwhile heat the gelatine with 1/4 C water and dissolve well so that no lumps remain.
Mix the mango pulp with the sugar and add the gelatine to it.Bring it to room temperature and add the coconut milk or cream to it and mix with a spatula.
Whip the whipping cream with sugar till its stiff and standing in peaks.
Fold in the cream with the mango coconut mixture with the cut and fold method making sure not to mix it vigorously.The mix will be of a thick consistency.
Pour the mixture into the cold biscuit crust and level it from all sides.
Garnish it with the sliced mangoes in a rosette design and keep it covered in the fridge for 4 to 5 hours or overnight for it to set properly.
For the design, arrange the slices on the top starting from the center and fanning them outwards to mimic a rose petal pattern. There are lot of you tube videos which will help you replicate the pattern.
Before serving carefully push the bottom of the pan to release the tart from the sides. Dust some icing sugar on the tart before serving.