Place gingersnaps in a food processor 20 at a time; grind to a fine crumb. Place the crumbs in large bowl and add melted butter and salt. Stir by hand until combined. Press evenly into the bottom of an ungreased 13x9x2 inch baking pan and bake for 10 minutes.
Meanwhile, place milk or half and half in a small microwave safe bowl. Microwave about 15 seconds or until just warm; stir in coffee powder until dissolved.
In the bowl of an electric mixer, beat cream cheese, sugar, vanilla and coffee mixture on medium speed until fluffy. In another small microwave safe bowl, microwave semi-sweet chocolate morsels for about 30 seconds, until just melted. Beat in melted chocolate. Add eggs one at a time, beating after each addition until just combined.
Evenly spread cream cheese mixture over crust and bake for 18-22 minutes or until set. Cool on a wire rack for 15 minutes. Using a small sieve, dust the top of the cheesecake with dark cocoa powder. Let stand at room temperature to cool for 45 minutes. Refrigerate for at least 2 hours before cutting into squares. Serve squares with whipped cream. Store in refrigerator.