01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - Process 4.25 oz pistachios in a food processor until finely ground. Reserve 1-2 tbsp for garnish.
03 - Sift flour, baking powder, and salt into a bowl. Stir in ground pistachios until evenly distributed.
04 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 3 minutes.
05 - Incorporate eggs one at a time, beating thoroughly after each addition. Blend in vanilla extract.
06 - Add dry ingredients in two batches, alternating with milk. Begin and end with the flour mixture, mixing just until combined.
07 - Distribute batter evenly among prepared cupcake liners, filling each about two-thirds full.
08 - Bake for 18-20 minutes until a toothpick inserted into the center emerges clean. Allow cupcakes to cool completely before frosting.
09 - Finely grind 3.5 oz pistachios in a food processor. A slightly coarse texture is acceptable for added crunch.
10 - Beat butter until smooth and creamy. Gradually incorporate powdered sugar, mixing until fully combined.
11 - Blend in ground pistachios, vanilla, salt, and 2 tbsp milk. Whip until fluffy, adding additional milk as needed to achieve spreading consistency.
12 - Pipe or spread buttercream onto cooled cupcakes. Garnish with reserved ground pistachios.