Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.

In a medium bowl, whisk together all-purpose flour, ground pistachios, baking powder, baking soda, and salt until well combined.

In a large mixing bowl, cream butter and sugar together until light and fluffy, about 3-5 minutes.

Incorporate eggs one at a time, followed by vanilla extract, mixing until smooth.

Gradually combine the dry mixture with the wet mixture, alternating with milk and sour cream.

Fill each cupcake liner about ¾ full with batter and tap the muffin tin to remove air bubbles.

Bake for 18-20 minutes until a toothpick comes out clean.

Cool cupcakes in the tin for 5 minutes, then transfer to a wire rack to cool completely.

Beat the softened butter in a mixing bowl until creamy, then gradually add sifted powdered sugar and heavy cream until fluffy.

Frost each cooled cupcake with vanilla buttercream and top with chopped pistachios and optional gold leaf.