Add instant pudding mix and mix to a medium mixing bowl. Whisk together for 2 minutes until thickened and all lumps are gone.
Refrigerate for at least 1 hour until the pudding is set. (If chilling longer than 1 hour, cover the pudding with plastic wrap so it's touching the surface. This will prevent a skin from forming.)
In another mixing bowl, beat whipping cream, vanilla, and powdered sugar until medium peaks form. Mix in peanut butter until well combined and smooth.
Chop the Snickers bars into small pieces. (I cut the bars into slices and then cut each slice in half.)
Assembly: Layer parfait in dessert cups starting with pudding on the bottom topped with peanut butter mousse, and then some candy bar pieces. Repeat layers in each cup. Serve immediately.
Notes
Recipe yield and nutrition will vary depending on the size of your serving cups.This recipe can make two large parfaits (as pictured). However, my family is only able to eat half of a big parfait before they tap out. I make four smaller parfaits instead most of the time.