Wrap 2 layers of foil around the outside of a 10" springform pan making sure to cover the bottom and sides.
If you aren't using a non-stick pan, spray pan liberally with cooking spray
Preheat oven to 300º.
Use an electric mixer with paddle attachment, combine cream cheese & butter & beat until smooth.
Add eggs one at a time until blended.
Beat in sour cream
Add sugar & cornstarch & beat until very smooth
Fold in crushed Oreo cookies
Pour into prepared chilled pan
Top with crushed cookies
Place in a large roasting pan
Place pan in preheated oven & carefully pour boiling water into roasting pan to fill halfway up sides of cheesecake pan.
Bake 2 - 2.5 hours, or until cake is lightly browned on top. I baked 2 hours & then turned on my convection for another 12 minutes.
Remove from water bath & foil & cool at room temperature
Cover & refrigerate overnight
When ready to serve, drizzle with chocolate sauce