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 together flour, baking powder, and salt in a bowl. Stir in the ground pistachios.
04 - Beat 3.9 oz softened butter and 5.3 oz granulated sugar in a large bowl until light and fluffy, approximately 3 minutes.
05 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
06 - Add dry ingredients in two batches, alternating with ½ cup milk, starting and ending with flour mixture.
07 - Divide batter evenly among prepared cupcake liners.
08 - Bake for 18-20 minutes until a toothpick inserted in the center comes out clean. Cool completely before frosting.
09 - Finely grind 3.5 oz pistachios in a food processor, leaving slightly coarse texture preferred.
10 - Beat 7.9 oz softened butter until smooth and creamy. Add powdered sugar gradually, beating until fully combined.
11 - Mix in ground pistachios, vanilla, pinch of salt, and 2 tbsp milk. Beat until fluffy, adding additional milk as needed for desired consistency.
12 - Pipe or spread buttercream onto cooled cupcakes. Sprinkle with reserved ground pistachios.