1-In a medium mixing bowl, combine vanilla: In a medium mixing bowl, combine vanilla pudding mix with cold milk, stirring to whisk out any lumps. Set aside to thicken for 5 minutes.
2-In the meantime, combine ½ cup heavy: In the meantime, combine ½ cup heavy whipping cream and 3 tbsp powdered sugar. Whip to form stiff peaks, then fold the whipped cream into the thickened vanilla pudding.
3-Transfer the vanilla pudding mixture into a: Transfer the vanilla pudding mixture into a piping bag or Ziploc bag and set in the fridge.
4-Pour chocolate chips and the remaining heavy: Pour chocolate chips and the remaining heavy whipping cream into a microwave safe bowl and microwave for 45 seconds or until the cream is hot but not boiling.
5-Stir with a rubber spatula until the: Stir with a rubber spatula until the chocolate is melted and smooth. Transfer to another piping bag or Ziploc bag and set aside.
6-Lay half of the nilla wafers (flat: Lay half of the nilla wafers (flat side facing up) on a baking sheet lined with parchment paper or a silicone baking mat.
7-Cut off one end of the vanilla: Cut off one end of the vanilla pudding bag, then squeeze a dollop of the nilla pudding onto each vanilla wafer. Lightly press another nilla wafer on top to sandwich the filling.
8-Cut off one end of the ganache: Cut off one end of the ganache bag and squeeze a dollop on top of each cookie sandwich. If needed, go back in with a spoon to smooth out the surface.
9-Transfer to the fridge to chill or: Transfer to the fridge to chill or enjoy immediately!