Preheat oven to 375 degrees
Put cookies into a food processor and pulse until crumbly
Press cookies into bottom of a greased 9" spring form pan
Put spring form pan in freezer
Beat together cream cheese and sugar until smooth
Add eggs, vanilla, and cornstarch and beat until smooth
Stir in sour cream
Pour filling into spring form pan
Bake at 375 degrees for ten minutes
Lower oven temperature to 200 degrees and bake forty five minutes
Crack oven door and allow to cool for 3 hours
Cover with plastic and refrigerate cake for 2 hours or up to 2 days until ready to top
Melt six ounces of semisweet chocolate chips in the oven at 200 degrees for ten minutes
Stir chocolate together, put in a piping bag, and pipe chocolate on to cake