Preheat oven to 325 degrees. Coat an 8-inch square baking pan with cooking spray. Line with two crisscrossed pieces of parchment or wax paper, spraying between sheets. Spray lined pan; set aside.
Process cookies in a food processor until finely ground. Gently press crumbs into bottom of prepared pan (do not rinse processor bowl).
Blend cream cheese and sour cream in food processor until smooth, scraping down sides of bowl as needed. Add cocoa, cornstarch, sugar, egg, and egg white; process until smooth. Pour into pan; sprinkle with chocolate chips.
Bake until just set, 35 to 40 minutes; cool completely in pan. Refrigerate at least 1 hour. Invert onto a tray; peel off paper, and reinvert crust side down. Cut into 9 squares.