Grease a 10 inch spring-form cake pan and line bottom and sides with parchment paper.
Melt butter and pour into a large bowl.
Sift cocoa into butter and stir in sugar.
Add eggs one at a time to mixture.
In a separate bowl, combine flour, Baking powder, and salt. Add to cocoa mixture and mix until all combined.
Stir in white chocolate chips.(If using).
Pour into prepared pan and bake for 25-35 minutes until firm. (I usually start checking at 25 minutes because I don't want it to overcook! Every oven is different. You want it to be firm, but not overcooked- almost moist but not quite).
Cool completely before filling.
Place chocolate chips in a bowl over a pot of gently simmering water until melted. Remove from heat and set aside.
Beat cream cheese until smooth and fluffy with electric beaters or in a mix master.
Slowly add sugar while mixing and beat in vanilla.
Pour in whipping cream and whip on high speed until mixture becomes firm and holds a peak.
Scrape melted chocolate into mixture until all combined, scraping the sides of the bowl with a spatula. Make sure you scrape down to the very bottom to see if you got it all mixed up!
Once all combined, scrape filling onto brownie layer-Spread evenly.
To garnish, sprinkle crushed Oreo cookies over top of cheesecake. OR drizzle the melted white chocolate over top, anyway you like! Make it look fancy, or make it look messy. It is your creation!
Chill cheesecake for a minimum of 3 hours(more is better) before slicing, to be sure it is fully set.
*HINT* I find it really hard to slice, so I use my Chef's Knife, run it under hot water for about 5-10 seconds and that makes it ALOT easier to cut!