Grind shelled pistachios in a food processor until they reach a fine consistency, about 1-2 minutes.

In a large mixing bowl, combine ground pistachios, all-purpose flour, baking powder, and salt. Whisk for about 1 minute.

In a separate bowl, cream together unsalted butter and granulated sugar for approximately 3 minutes until light and fluffy.

Add eggs one at a time, mixing well after each. Pour in whole milk, vegetable oil, and vanilla extract and mix until combined, about 1-2 minutes.

Fold the dry flour mixture into the wet batter using a spatula until just combined.

Grease three 8-inch round cake pans and divide the batter evenly between them. Bake at 175°C (350°F) for 22-25 minutes.

Allow cake layers to cool in the pans for about 10 minutes before transferring to a wire rack to cool completely.

Whip the heavy cream until soft peaks form, then add mascarpone cheese, powdered sugar, and vanilla extract and whip until thick and creamy.

On a serving plate, place one cooled cake layer, spread mascarpone cream, repeat with the second layer, then frost the top and sides of the cake.

Refrigerate the finished cake for a minimum of 2 hours before serving to enhance flavors.