1) Line a small baking sheet with parchment paper. Add banana slices to the parchment in rows to make a square shape. You want to make sure all your banana slices are touching.
2) Add another layer of parchment paper on top and use the bottom of a glass cup to smush the bananas slightly so they become one banana layer.
3) Use a spoon to spread the nut butter over the banana slices to make a layer.
4) Place chocolate chips into a microwave-safe bowl and melt in the microwave in 30-second increments, stirring between each. It shouldn’t take more than 1-2 minutes in total.
5) Drizzle melted chocolate over the nut butter and spoon or spread the chocolate into a thin layer.
6) Sprinkle the pistachios over the chocolate layer and place in the freezer overnight.
7) Remove from the freezer, break or cut into pieces and enjoy! Store any leftover bark in the freezer for up to a month.