Stir gingernut crumbs and the melted butter in a small saucepan until the crumbs are evenly coated. Lightly press crumb mixture over bottom and side of a 23 cm pie pan.
Whisk pudding mixes and milk in a medium bowl until thick and blended. Stir in pumpkin purée, cinnamon, ginger and nutmeg. Spread evenly over gingernut crust. Garnish top with pecan halves, if using. Cover and refrigerate for at least 5 hours or overnight.
Instead of a whisk, you can use a food processor or blender to combine the filling ingredients for this pie. Short on time? Make the pie even more quickly by using a store-bought, prepared crust.