Instructions:
- Prepare the Pistachio Paste: Process the raw pistachios in a food processor until a fine, slightly oily paste forms. Set aside.
- Temper the Yolks: In a medium bowl, whisk the egg yolks, 1/2 cup sugar, cornstarch, and salt until pale and creamy (ribbon stage).
- Heat the Milk: In the saucepan, combine the milk and the remaining 2 tablespoons of sugar. Heat over medium heat until just simmering around the edges.
- Temper the Eggs: Slowly ladle about one cup of the hot milk into the yolk mixture while constantly whisking vigorously to prevent scrambling.
- Cook the Cream: Pour the tempered yolk mixture back into the saucepan with the remaining milk. Whisk constantly over medium-low heat until the mixture visibly thickens and begins to bubble (about 1–3 minutes after the first bubble).
- Incorporate Flavour: Remove from heat. Immediately whisk in the prepared pistachio paste and vanilla extract until fully incorporated and the colour is uniform.
- Enrich and Cool: Whisk in the cold butter cubes, one at a time, until melted and emulsified, adding a lovely gloss to the cream.
- Chill Rapidly: Strain the cream through a fine-mesh sieve into a shallow, clean bowl. Press plastic wrap directly onto the surface of the cream to prevent a skin from forming. Refrigerate for a minimum of 3 hours.
- Final Whip: Once fully chilled and firm, remove the plastic wrap. Give the cream a vigorous whisk or beat briefly with an electric mixer to restore its smooth, pipeable consistency before using.