01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - In a food processor, finely grind 4.25 oz pistachios for the cupcakes. Reserve 1–2 tbsp for garnish.
03 - In a bowl, sift together flour, baking powder, and salt. Stir in the ground pistachios.
04 - In a separate large bowl, beat the butter and sugar until light and fluffy (about 3 minutes).
05 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
06 - Add the dry ingredients in two batches, alternating with milk, starting and ending with flour mixture.
07 - Divide the batter evenly among cupcake liners.
08 - Bake 18–20 minutes until a toothpick inserted in the center comes out clean. Cool completely.
09 - For the pistachio buttercream, grind 3.5 oz pistachios finely (can leave slightly coarse for texture).
10 - Beat the butter until smooth and creamy. Add powdered sugar gradually, beating until combined.
11 - Mix in ground pistachios, vanilla, a pinch of salt, and 2 tbsp milk. Beat until fluffy, adding extra milk for desired consistency.
12 - Pipe or spread the buttercream onto cooled cupcakes. Sprinkle with reserved ground pistachios.