Preheat oven to 300 degrees F. In a food processor, combine the Oreo and Grasshopper cookies. Pulse until fine crumbs form. Add the butter and pulse a few times, just until crumbs become moistened. Press the cookie crumbs into the bottom of a 9-inch springform pan. Set aside
In a large bowl, using a hand-held mixer, beat the cream cheese on medium speed until light and fluffy, about 3 minutes. Add the sweetened condensed milk and mix until just incorporated. Add the eggs and mix until incorporated. Add the Crème de Menthe, peppermint extract and food coloring and mix well.
In a small bowl, combine 1 cup of the chocolate chips with the flour. Stir to coat. Add the flour-coated chocolate chips to the cream cheese mixture and stir. Pour the mixture into the prepared springform pan. Top with ½ cup of chocolate chips. Place the pan on a baking sheet and bake in the preheated oven for one hour.
Remove pan from oven and immediately use a knife to separate the cheesecake from the edge of the pan all the way around. Let cool. Refrigerate until ready to serve. Just before serving, in a small bowl, combine ½ cup of the chocolate chips with the milk and microwave on high for 30 seconds. Stir until smooth. Microwave in 15-second intervals, if needed, stirring after each interval, until smooth. Drizzle the melted chocolate over each slice of cheesecake, and serve.