Preheat oven to 325° F. Line the bottom of a 9-inch springform pan with parchment paper. Grease the sides of the pan with butter.
In a food processor, pulse graham cracker sheets until fine crumbs form, about 10 one-second pulses. Add sugar and melted butter. Pulse until well combined, about 5 one-second pulses.
Transfer mixture to the prepared pan and use the bottom of a measuring cup to firmly press the graham crackers down. Bake for 10 minutes. Let the crust cool slightly, then wrap the bottom and sides of the pan with two layers aluminum foil for the water bath. Keep the oven on.
S’mores Cheesecake Filling
In the bowl of a stand mixer fitted with a paddle attachment, beat cream cheese and sugar on medium-high speed until smooth, about 3 minutes.
Add the sour cream, vanilla and lemon juice. Beat until combined, about 1 minutes. Add the eggs and egg yolk, one at a time, mixing well after each addition. Scrape down the bottoms and sides of the bowl to make sure the mixture is uniform. Stir in the chopped Fannie May S’mores Snack Mix by hand.
Transfer mixture to pre-baked graham cracker crust. Spread the top evenly and tap the pan on the counter a few time to remove any air bubbles.
Fill a roasting pan 1 inch high with warm tap water. Place the roasting pan in the oven, then place the cheesecake in the roasting pan.
Bake the cheesecake at 325 F for one hour or until the filling only jiggles slightly in the center when gently shaken. Turn off the oven, crack the door open and let the cheesecake cool in the oven for 1 hour. Remove the cheesecake from the roating pan and chill it in the refrigerator for 4 hours or overnight.
When ready to serve, remove the sides of the springform pan. Garnish cheesecake with additional chopped Fannie May S’mores Snack Mix and enjoy. Store cheesecake covered in the refrigerator for up to 3 days.