In a stand mixer with a whisk attachment, or using a hand held mixer, whip 1 1/4 cup whipping cream until it forms stiff peaks (about 5 minutes). It is important to have stiff peaks here so make sure you whip it well. Set aside.
Now in a new bowl in the stand mixed with a paddle attachment, beat three bricks of full fat cream cheese and 1/4 cup sugar until smooth and creamy (about 2-3 minutes).
Scrape down the sides of the bowl, add ½ cup mango pulp, 1/4 cup sour cream, 2 tsp lemon juice and 1 tsp vanilla extract. Beat to combine, stopping the mixer to scrape down the sides occasionally. Make sure there are no lumps of cream cheese in the mixture.
Using a spatula, gently fold in the whipped cream into the mango cheesecake mixture a little at a time until just combined. Mix carefully so you don't deflate the whipped cream!
Pour the mango cheesecake mixture into the prepared pie crust(s) making sure the top is smooth. Refrigerate for at least 8 hours, but ideally for 12 hours.The longer it has to chill the better the cheesecake mixture will set. If you are making this ahead to freese, do not freeze immediately as it needs to set in the fridge for at least 8 hours before you freeze it so the texture is perfect.
Just before you are ready to serve, top with mango slices and more whipped cream if you like, and serve chilled.