Combine cornflake crumbs and butter; press onto the bottom of a 9-in. square pan coated with cooking spray. Refrigerate for 10 minutes.
Meanwhile, in a small saucepan, sprinkle gelatin over cold water; let stand for 1 minute. Heat over low heat, stirring until gelatin is completely dissolved. Remove from the heat; set aside.
In a large bowl, beat cream cheese and sugar until smooth. Beat in the milk, Kahlua and gelatin mixture until blended. Gently fold in whipped topping; pour over crust. Cover and refrigerate for at least 4 hours or until firm.
Drizzle with melted chocolate; garnish with raspberries and mint leaves if desired.