Line a 9-in. square baking pan with foil and grease the foil. In a small bowl, combine the graham cracker crumbs, pecans and butter. Press into prepared pan; set aside.
In a large bowl, beat the cream cheese, sugar and sour cream until smooth. Add eggs and vanilla; beat on low speed just until combined. Pour over crust. Bake at 325° for 35-40 minutes or until center is almost set. Cool on a wire rack. Freeze overnight.
In a microwave, melt chocolate and shortening; stir until smooth. Cool slightly.
Using foil, lift cheesecake out of pan. Gently peel off foil; cut cheesecake into 1-1/4-in. squares. Work with a few pieces at a time for dipping; keep remaining squares refrigerated until ready to dip.
Using a toothpick, completely dip squares, one at a time, in melted chocolate; allow excess to drip off. Place on waxed paper-lined baking sheets. Spoon additional chocolate over the tops if necessary to coat. (Reheat chocolate if needed to finish dipping.) Let stand for 20 minutes or until set. Store in an airtight container in the refrigerator or freezer.