Prepare Pistachio Paste by blending shelled pistachios in a food processor until finely ground, then gradually add heavy cream to form a thick paste.

In a stand mixer, beat softened unsalted butter on medium-high for 7-9 minutes until fluffy and pale.

Gradually add the pistachio paste and vanilla extract to the whipped butter and mix until combined.

Slowly add sifted confectioner’s sugar while mixing on low speed, then increase to high and beat for 3-4 minutes.

Add green food coloring if desired, and mix until the color is evenly distributed.

If frosting is flat or soft, chill for 30 minutes, then re-beat until fluffy.

Store in an airtight container covered with plastic wrap if not using immediately.