In a heatproof bowl placed over a pan with gently simmering water melt together butter and chocolate. Remove the bowl from the heat and add in the cookie crumbs (crushed in a zipped bag with a rolling pin or in a food processor). Mix until well combined. Press the prepared crust onto the bottom of a 19-20 cm springform pan. Let the pan sit in the fridge while preparing the cheesecake filling.
In a small saucepan over medium heat combine chopped strawberries and sugar and bring to boil. Let simmer for about 30 minutes, mixing from time to time. When the mixture starts getting thick, remove from heat and let cool until room temperature.
In a large mixing bowl whip the sour cream with vanilla and powdered sugar for 5 minutes at high speed. Add cream cheese and beat at a lower speed until well combined.
Sprinkle the gelatine over 50 ml water and let stay for 5-10 minutes.
In a small heatproof bowl over a pan with gently simmering water combine the bloomed gelatine with the rest of the water (100 ml). Whisk continuously until the gelatine is completely dissolved.
With the mixer on high speed, add the gelatine mixture into the cheesecake filling. Beat until completely absorbed.
Assemble the cheesecake:
Spoon a small part of the white filling in the prepared pan, over the crust.
Add about 1/3 of the strawberry mixture to the cheesecake filling and beat until well combined.
Spoon some of of the coloured filling over the white one, so that it covers it completely.
Add about half of the remaining strawberry mix to the cheesecake filling and beat until well combined. Spoon another layer of filling in the pan (it should be slightly more intensive pink than the previous layer).
Add the rest of the strawberry mix to the cheesecake. Beat well until combined. Pour/ spoon the rest of the strawberry filling in the pan.
Cover the cheesecake with cling film and let stay in the fridge for at least 4-6 hours.