Pour the crumbs into the pan. Use a flat-bottom glass to press the crust onto the bottom and up the sides about 1-inch/2.5 cm up the sides of the pan.
Refrigerate the crust for at least 30 minutes while you make the cheesecake filling.
Cheesecake
In a small bowl, mix matcha powder and 2 tbsp hot water until well combined. Set aside.
In a small bowl, bloom gelatin powder with 1 1/2 tbsp water for 5 minutes. Heat in a microwave or over a water bath until the gelatin is dissolved.
Using a hand mixer or stand mixer fitted with the whisk attachment, beat the cream cheese, confectioners' sugar, and vanilla extract until smooth and well combined.
While the mixer is running, pour the dissolved gelatin into the cream cheese mixture and beat until well combined.
Add matcha mixture and beat until well combined.
Add heavy whipping cream and mix on low speed with your mixer just until well combined. Fold in the chopped Oreos.
Assemble
Pour the cheesecake batter onto the chilled crust. Carefully spread it around into one even layer. Use a spatula to smooth the top.
Cover tightly and transfer back to the refrigerator to chill for at least 4 hours or overnight.
Release the cheesecake from the mold. Peel the parchment paper/acetate sheet.
Pipe whipped cream on top and decorate with mini Oreos and rosemary.