Combine the crushed graham crackers and melted butter in a bowl, and mix well.

Press the mixture into the bottom of muffin tins or mini cheesecake molds, making sure it is firm.

Refrigerate the crust for at least 15 minutes to firm it up.

In a large bowl, beat the softened cream cheese and powdered sugar together until smooth.

In a separate bowl, whip the heavy cream until soft peaks form, then gently fold it into the cream cheese mixture.

Add the ground pistachios and vanilla extract to the mixture, and fold until combined.

Spoon the filling into the prepared crust, smoothing the tops with a spatula.

Chill the assembled cheesecakes in the refrigerator for at least 4 hours, or until set.

Once set, carefully remove the mini cheesecakes from the molds, and garnish with pistachio halves.