Preheat the oven to 325 degrees and grease a 9 inch springform pan. You will need a large roasting pan that’s bigger and longer than the springform pan. (I use the aluminum foil disposable ones). If you are not sure about your springform holding up in water, you can wrap the outside of the springform pan in heavy duty aluminum foil from bottom up to the sides. (I recommend wrapping the outside of the springform in foil before adding the crust and cheesecake batter.)
In a small sauce pot, over medium to medium-low heat, combine raspberries, vanilla, lemon juice, and sugar. Mix well and cook, over medium heat and covered for about 10 minutes.
Smash all the berries with a wooden spoon and cook for another 10 minutes over medium-low heat.
Whisk in cornstarch with a little bit of cold water and stir it into the raspberry mixture. Stir for a couple of minutes, until the mixture thickens.
Strain the mixture through a fine mesh strainer to get rid of the seeds and leftover skin. Use a wooden spoon to scrape and stir the raspberry mixture while straining to get the most out.
Set it aside for a few minutes to cool while preparing the cheesecake.
Pulse Oreo cookies in the food processor or blender until it's just crumbs.
In a small bowl, combine cookie crumbs and melted butter until evenly incorporated.
Press cookie crust mixture into the pan, evenly, all over the bottom and about half way up the side.
Start beating cream cheese and sugar on medium-high speed until smooth, about 2 minutes.
Add vanilla extract, and sour cream. Mix until combined.
Add eggs, one at the time, beating after each addition. Scrape sides and bottom of the bowl and beat until all incorporated.
Lower speed and add corn starch. While on medium-low speed, pour in heavy cream. Mix until all combined, scrape the sides and bottom of the bowl and mix again until smooth.
Melt white chocolate bar in the microwave or in a double boiler, according to the melting instructions on the label. (If melting in the microwave, make sure to melt on half the power and in 30 second increments.)
Pour in melted chocolate into the cheesecake while it's mixing. Scrape side and bottom of the bowl and make sure everything is evenly incorporated.
Pour the cheesecake batter into the springform, over the crust.
Spoon about 2/3 of the raspberry topping over the top of the cheesecake and carefully swirl it into the cheesecake but don't mix. You can use the thin handle of a wooden spoon or something similar to swirl. (Reserve about 1/3 of the raspberry topping to top off cooked cheesecake when decorating.)
Baking the cheesecake:
Place roasting pan into the oven and place the cheesecake springform pan inside the roasting pan. Carefully add water to the roasting pan, about half way up the side of the springform.
Bake for 85-90 minutes. Turn off the oven and open the oven door half way. Let cheesecake rest for about 10-15 minutes and take it out of the oven (out of the roasting pan and carefully take off the foil).
Let it rest for 20 minutes on the counter and then gently run a greased butter knife between sides of the cheesecakes and the springform to carefully separate it. (You don't actually have to take the cheesecake out of the pan until ready to add topping.)
Cool cheesecake on the counter for an hour.
Cover the pan with saran wrap and place the cheesecake in the refrigerator. Refrigerate for at least 4 hours before adding the frosting.
Break up white chocolate bars and melt them according the to package instructions.
Beat cream cheese with an electric mixer for a couple of minutes.
Drizzle in melted white chocolate while continuing to beat cream cheese. Mix well.
With mixer turned off, fold in whipped topping gently until all combined.
Spread about a third of the white chocolate frosting over the top of the cheesecake.
Transfer the rest of the storing into a piping bag fillet with a decorating tip (I use 1M) and decorate with flowers or swirls around the cheesecake top.
Spoon remaining raspberry topping into the center. Top it all off with white chocolate curls.
TIP: Super easy cheater way to make chocolate curls is to use a vegetable peeler and slowly "peel" the chocolate bar. You can also to shave the chocolate bar on a box grater to make some chocolate shavings. (Note: it's easier to make chocolate curls with room temperature chocolate, not cold.)