Preheat your oven to 175°C (350°F). Line three 8-inch round cake pans with parchment paper and lightly grease the sides.

Finely grind the shelled pistachios in a food processor until they resemble flour. In a large bowl, whisk together the ground pistachios, flour, baking powder, and salt.

In a large mixing bowl, beat the butter and sugar on medium speed until light and fluffy, about 3 minutes. Scrape down the sides of the bowl.

Add the eggs one at a time, mixing well after each addition. Then stir in the milk, vegetable oil, and vanilla extract until just combined.

Gently fold the dry mixture into the wet ingredients until just combined to maintain airiness.

Divide the batter among the prepared pans and bake for 22–25 minutes, or until a toothpick inserted in the center comes out clean.

Allow cakes to cool in the pans for about 10 minutes, then transfer to a wire rack to cool completely. Meanwhile, whip the heavy cream with mascarpone, powdered sugar, and vanilla until thick and creamy.

Assemble the cake by placing one layer on a serving platter, spreading mascarpone cream between layers, and frosting the top and sides with remaining cream.

Refrigerate for at least 2 hours to set the cream. Garnish with chopped pistachios before serving.