Place pistachios in a large saucepan. Cover with water, bring to a boil and cook 2 minutes. This step is critical to soften the pistachos for a silky smooth En texture. Drain the pistachios.

Place drained pistachos in a food processor and blend until smooth. This wii take about 2 minutes, stopping to scrape down sides a few times.

Add butter and blend until smooth

Add one cup of the confectioner's sugar slowly in batches , blending until very smooth

In a large bowl beat cream to soft peaks, add vanilla and remaining 1 cup confectioner's sugar

Add a few spoonfulls of pistachio puree to cream, beat it in carefully. Don't overbeat. When cream is thickened fold in remaining pistacho puree to blend. At this point I added some green food coloring to get the classic green color, my pistachos were natural un colored pistachos

Refrigerate firm up for easy spreading or piping