Prepare crust: In a food processor, add graham crackers, sugar and butter and pulse until blended. Press mixture evenly into a 9" square baking pan. Bake for approximately 7-10 minutes. Cool on a wire rack.
Increase oven temperature to 400°F.
In a mixing bowl, beat eggs, sugar, salt, nutmeg and vanilla. Set aside.
In a saucepan over medium heat, add holiday custard. Stir often to prevent scorching, cooking until bubbles forms around the edges. Remove from heat and slowly blend in egg mixture, then pour over crust.
Bake for approximately 30-35 minutes. Insert a knife in the center, if it comes out cleanly, remove from oven.
Cool completely on a wire rack.
Before serving top with hazelnut spread and sprinkle with white chocolate shavings and chopped hazelnuts.