Make the crust: To the bowl of a food processor fitted with the blade attachment, add one package of Manner wafer cookies, and pulse just to break the cookies down to medium-fine crumbs, taking care not to over process. Transfer the crumbs to a medium bowl, then repeat with the remaining two packages of wafers. To the bowl of crumbs, add the butter, hazelnuts, and salt, then use a fork to blend until the mixture is thoroughly moistened and holds together when squeezed in the palm of your hand.
Preheat an oven (with one of its racks positioned in the center) to 325° F. Lightly grease the bottom, but not the sides, of a 9-inch aluminum or glass pie plate with nonstick spray or oil. Sprinkle the crumb mixture over the bottom of the pie plate, then place a piece of plastic wrap over the crumbs, and press them into an even layer, working the mixture into the corners of the plate and evenly up the sides. Use the bottom of a ¼ cup measuring cup or glass to smooth the crumbs into place. Transfer to the freezer until the crust is firm and set, at least 15 minutes or overnight.
Retrieve the pie shell from the freezer, place it on a large baking sheet, remove the plastic film, then immediately transfer to the oven and bake until just set and lightly browned, checking it towards the end, 12–14 minutes. Set aside to cool completely.
Meanwhile, prepare the filling: To a heavy bottomed saucepan over medium heat, add the frozen raspberries, sugar, and salt. Cook, stirring occasionally, until the mixture comes to a boil. In a small bowl, stir together the cornstarch and 1 tablespoon cold water, then add this slurry to the boiling berry mixture. Continue cooking, stirring frequently, until thickened, about 4 minutes. Remove from the heat, then stir in the raspberry preserves and vanilla. Set aside to cool to room temperature.
When the raspberry filling is cooled, pour it into the pie shell and use an offset spatula or the back of a spoon to smooth into an even layer. Cover with plastic wrap and refrigerate while you prepare the mascarpone cream.
In a large bowl, use a silicone spatula to fold together the mascarpone and sour cream. Slowly drizzle in the honey while folding, just to combine, then fold in the hazelnuts.
Retrieve the pie from the fridge. Spoon the mascarpone cream over the raspberry filling then use an offset spatula or the back of a spoon to smooth. Cover loosely with plastic wrap and refrigerate until the mascarpone cream is firm, at least 3 and up to 8 hours. Just before serving, remove the plastic wrap and garnish the pie with fresh raspberries. Serve cold; cover and refrigerate any leftovers for at least 3 hours and up to 3 days.