In a small bowl, combine the Jello pistachio instant pudding mix with your milk. Whisk for approximately 2-3 minutes, then allow to set. Once set, transfer it onto the top of a bundt cake and garnish with the remaining pistachios.
Notes
This recipe yields a more glaze like frosting. For a fluffy pistachio cake frosting, use heavy whipping cream in place of the milk. Mix the pudding and cream on medium high speed in a mixer for 2-3 minutes until peaks form. Frost.