Preheat your oven to 350°F (175°C). Grease and line three 9-inch round cake pans with parchment paper.

In a large mixing bowl, cream together the softened unsalted butter and granulated sugar using an electric mixer on medium speed for about 3-4 minutes.

Add the large eggs one at a time to the mixture, fully blending each egg before adding the next. Mix in the vanilla extract until thoroughly combined.

In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Gradually add this to the wet ingredients, folding gently to combine.

Evenly divide the cake batter among the prepared pans and bake for 25-30 minutes, or until a toothpick inserted comes out clean.

Remove the pans from the oven and let them cool for about 10 minutes before transferring the cakes to a wire rack to cool completely.

While the cakes cool, prepare the frosting by beating heavy cream until soft peaks form and then folding in the mascarpone cheese, pistachio extract, and powdered sugar.

To assemble the cake, place one cooled layer on a serving platter, spread frosting on top, add the second layer and repeat. Frost the final layer generously.

Sprinkle chopped pistachios over the top and sides for presentation, and add fresh mint leaves to garnish.