In a mixing bowl, combine the creamy peanut butter and powdered sugar. Mix until well blended and smooth.
In a small saucepan, heat 2 tablespoons of cold water and sprinkle the gelatin over it. Let it bloom for a few minutes, then gently heat over low heat until fully dissolved. Allow to cool slightly.
In another bowl, whip the heavy cream and vanilla extract together until soft peaks form.
Once the gelatin has cooled, fold it into the peanut butter mixture until fully incorporated.
Gently fold the whipped cream into the peanut butter mixture until everything is well combined and has a light, fluffy consistency.
Spoon the peanut butter filling into the prepared graham cracker crust, smoothing the top with a spatula.
Refrigerate the pie for at least 4 hours or until set (overnight is best).
Once set, slice and serve chilled. Garnish with chocolate shavings or crushed peanuts if desired.